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Decentralized software licensing

Dotlicense is an Ethereum ERC721-based software licensing framework.

Built by Dotta and contributors


Dotlicense is a set of smart contracts and JavaScript tooling to sell and verify software licenses (e.g. in-app-purchases or feature access tokens) using Ethereum. It supports both single purchase and (prepaid) subscriptions.

The licenses are ERC721-compatible Tokens. The client app holds the private key that owns the token.

The benefits are:

  1. Piracy deterring -- Because the private key is used to validate the license, owners are dis-incentivized to share that key. Because if the key is shared, for example, on a file-sharing site the license can be transferred, stolen, and sold.
  2. Surveillance free -- There is no "license server" tracking the user. Ownership of the token is validated by any Web3 provider (e.g. Infura or even a self-hosted node)
  3. Scarce -- The number of licenses available for a given product can be limited
  4. Transferable -- Users can transfer or resell their licenses (e.g. they can be auctioned on sites such as Rarebits or OpenSea)
  5. Cryptocurrency-based -- Normal-cryptocurrency benefits apply such as near-instant payments, permissionless, decentralized ownership, etc. No approvals, Stripe, Shopify store, or bank account necessary.

It is designed for software licenses in desktop or mobile apps. (And there is discussion about using it for subscription web apps.)


  • Multiple products - Each product has its own inventory levels and total supply, housed in one contract
  • Subscriptions - Products can (optionally) expire and be renewed by paying additional funds
  • Affiliate program - Affiliates can get a cut of sales they refer with individual, whitelisted rates (including recurring affiliate revenue with subscriptions)
  • Roles-based permissions - The store has three roles: CEO, CFO, and COO
  • Full ERC-721 Compatibility - Each license issued is also an ERC-721-compatible token
  • CLI Admin Tools - With Ledger hardware wallet support
  • Embeddable Web3 Checkout - UMD JavaScript checkout button with Metamask support


Dotlicense is being used in Dottabot, a cryptocurrency trailing-profit stop bot built with Electron.


Dotlicense is split into several packages:

  • dot-license-contracts holds the Solidity smart contracts that manage the sale and ownership of tokens
  • dot-license-cli is the CLI admin tools for managing the smart contracts
  • dot-license-checkout a customer checkout widget for purchases using Metamask and React
  • dot-license-verifier (open-sourced soon) is a JavaScript wrapper library for client apps that need to list products that are owned, verify the licenses, etc.

Additionally, this repo stores some utilities we've built along the way such as:

  • dot-abi-cli - Generates a DApp CLI scaffold from an ABI (with Ledger support)

Purchase Model

There are two main models in the contracts:

  • The Product - which defines a feature or set of features and
  • The License - (the token) which defines ownership of an instance of a Product

And during operation we have:

  • The user (our customer) who is buying access to the features and
  • The client (our software) which runs our application and enables new features on verified ownership

The Products

Products have:

  • an id
  • a price
  • the quantity available
  • the totalSupply
  • the quantity sold

And optionally, if the product is a subscription, it may have:

  • a renewal interval, e.g. 1 month or 1 year in seconds
  • a renewable setting, which may be used to disable renewals of old plans

The client unlocks features of a given Product id if ownership of a License is proven.

When a new product is created, the totalSupply is fixed and cannot be changed. A totalSupply of 0 means "unlimited".

When a new product is created, the renewal interval is fixed and cannot be changed. An interval of 0 means "unlimited".

The executives can:

  • Create new Products
  • Change the price for future sales of a Product
  • Change the inventory amount available as long as it does not violate the totalSupply
  • Change the product's renewable status

The License

The License represents ownership of one unit of a Product. The License is the same as a "token" - they have the same ID and the two are used interchangeably.

Licenses have:

  • an id
  • a productId, which points to the Product this License is for
  • attributes (uint256), which are specific to this individual License
  • issuedTime, which is the time when this License was created (i.e. minted)
  • an owner

And optionally:

  • an expirationTime when this License expires
  • an affiliate address, who is credited for the original sale of this License

A License is created (that is, the token is minted) at time of sale. When a sale is made, the inventory for that Product is decremented and ownership is transferred to the assignee

An expirationTime of 0 means "does not expire".

The executives can:

  • Issue promotional (free) Licenses, within the bounds of the supply
  • Issue promotional (free) renewal of Licenses


The private key that owns the license must be readable by the client software.

In Dottabot this private key is:

  • generated automatically by the software on installation and
  • kept in OS secret storage (such as Keychain on Mac or libsecret on Linux).

In Dottabot, this means that while it is encrypted on disk, it is also readable by the software without user interaction. (It can also be deployed onto a VPS where a hardware wallet may not be available.)

Of course, this raises the problem of funds at purchase: often our users will have an existing wallet that they spend from (and it won't be our application's private key).

To deal with this issue, we require the user input the assignee address at purchase time (that is, the address controlled by the client software). When the token is purchased, ownership of the token is given to the private key controlled by our software.

This helps fulfill the piracy deterrence requirement by incentivizing the user to keep the license private.

Contracts Overview

Contract Inheritance Architecture

The smart contracts are split into modules.

Roles-based Permissions

Issuance of new products and unsold inventory levels is centrally controlled. There are three roles:

  • CEO
  • CFO and
  • COO

Some of the smart contract functions are open to anyone and some are restricted by role. The table below shows the permissions for each:

function CEO CFO COO anyone
LicenseOwnership (ERC721)

Dotlicense Checkout

dot-license-checkout is a UMD (or React-component) library which embeds a Metamask-enabled checkout.

// React Component 

const logo = require("path/to/logo.png");

const offers = [
    productId: '1',
    duration: ONE_YEAR,
    name: '1 year',
    price: 0.15
    productId: '1',
    duration: ONE_YEAR * 2,
    name: '2 years',
    price: 0.15 * 2

const config = {
  httpProviderURL: '',
  licenseCoreAddress: '0xc3e2f9aADc4B5c467E0668C2d690a999A91A1a5C'

  productSubheading="Unlimited License"

CLI Tools


The CLI Admin tool has the following commands:

$ node ./bin/dot-license-cli.js --help
Usage: dot-license-cli.js <command> [options]

  dot-license-cli.js affiliateProgram                                             Get the affiliate program address
  dot-license-cli.js approve <to> <tokenId>                                       Approves another address to claim for the ownership of the given token ID
  dot-license-cli.js approveAll <to>                                              Approves another address to claim for the ownership of any tokens owned by
                                                                                  this account
  dot-license-cli.js getApproved <tokenId>                                        Gets the approved address to take ownership of a given token ID
  dot-license-cli.js availableInventoryOf <productId>                             The available inventory of a product
  dot-license-cli.js balanceOf <owner>                                            Gets the balance of the specified address
  dot-license-cli.js ceoAddress                                                   Get the CEO's Address
  dot-license-cli.js cfoAddress                                                   Get the CFO's Address
  dot-license-cli.js clearInventory <productId>                                   clearInventory clears the inventory of a product.
  dot-license-cli.js cooAddress                                                   Get the COOs address
  dot-license-cli.js createProduct <productId> <initialPrice>                     createProduct creates a new product in the system
  <initialInventoryQuantity> <supply>
  dot-license-cli.js decrementInventory <productId> <inventoryAdjustment>         decrementInventory removes inventory levels for a product
  dot-license-cli.js disapproveAll <to>                                           Removes approval for another address to claim for the ownership of any
                                                                                  tokens owned by this account.
  dot-license-cli.js getAllProductIds                                             Get all product ids
  dot-license-cli.js incrementInventory <productId> <inventoryAdjustment>         incrementInventory - increments the inventory of a product
  dot-license-cli.js isApprovedForAll <owner> <operator>                     Tells whether an operator is approved by a given owner
  dot-license-cli.js licenseAttributes <licenseId>                                Get a license's attributes
  dot-license-cli.js licenseInfo <licenseId>                                      Get a license's info
  dot-license-cli.js licenseIssuedTime <licenseId>                                Get a license's issueTime
  dot-license-cli.js licenseProductId <licenseId>                                 Get a license's productId
  dot-license-cli.js name                                                         token's name
  dot-license-cli.js newContractAddress                                           Gets the new contract address
  dot-license-cli.js ownerOf <tokenId>                                            Gets the owner of the specified token ID
  dot-license-cli.js pause                                                        called by any C-level to pause, triggers stopped state
  dot-license-cli.js paused                                                       Checks if the contract is paused
  dot-license-cli.js priceOf <productId>                                          The price of a product
  dot-license-cli.js productInfo <productId>                                      The product info for a product
  dot-license-cli.js purchase <productId> <assignee> <affiliate>                  Purchase - makes a purchase of a product. Requires that the value sent is
                                                                                  exactly the price of the product
  dot-license-cli.js setAffiliateProgramAddress <address>                         executives *
  dot-license-cli.js setCEO <newCEO>                                              Sets a new CEO
  dot-license-cli.js setCFO <newCFO>                                              Sets a new CFO
  dot-license-cli.js setCOO <newCOO>                                              Sets a new COO
  dot-license-cli.js setNewAddress <v2Address>                                    Sets a new contract address
  dot-license-cli.js setPrice <productId> <price>                                 setPrice - sets the price of a product
  dot-license-cli.js setWithdrawalAddress <newWithdrawalAddress>                  Sets a new withdrawalAddress
  dot-license-cli.js symbol                                                       symbols's name
  dot-license-cli.js takeOwnership <tokenId>                                      Claims the ownership of a given token ID
  dot-license-cli.js tokensOf <owner>                                             Gets the list of tokens owned by a given address
  dot-license-cli.js totalSold <productId>                                        The total sold of a product
  dot-license-cli.js totalSupply                                                  Gets the total amount of tokens stored by the contract
  dot-license-cli.js totalSupplyOf <productId>                                    The total supply of a product
  dot-license-cli.js transfer <to> <tokenId>                                      Transfers the ownership of a given token ID to another address
  dot-license-cli.js transferFrom <from> <to> <tokenId>                           Transfer a token owned by another address, for which the calling address
                                                                                  has previously been granted transfer approval by the owner.
  dot-license-cli.js unpause                                                      Unpause the contract
  dot-license-cli.js withdrawBalance                                              Withdraw the balance to the withdrawalAddress
  dot-license-cli.js withdrawalAddress                                            Get the withdrawal address
  dot-license-cli.js info                                                         Describe contract info

  --web3              web3 provider url                                                                                   [default: "http://localhost:8545"]
  --from              from address
  --gasPrice          gas price in wei to use for this transaction                                                                   [default: "1000000000"]
  --gasLimit          maximum gas provided for this transaction                                                                         [default: "6500000"]
  --value             The value transferred for the transaction in wei
  --contract-address  address to contract                                                 [required] [default: "0xb4f53a030f9d088198cdb66b8ad95aa79a95868f"]
  --network-id        The network ID                                                                                                        [default: "101"]
  --ledger            use a ledger                                                                                                                 [boolean]
  --hd-path           hd-path (used for hardware wallets)                                                                          [default: "44'/60'/0'/0"]
  --help              Show help                                                                                                                    [boolean]
  --version           Show version number                                                                                                          [boolean]

Objections and Risks

Because licenses are verified on the client, this framework may be susceptible to at least two attacks: cracking and spoofing.


Like any desktop, mobile, or client-run app it may be possible for a determined hacker to patch the binary in such a way as to bypass the verification mechanism. Over time, we expect to improve our deterrence methods, but cracking is always a risk.


Because this software uses the Ethereum blockchain to verify ownership of a license-token, one could "spoof" ownership by directing their Web3 provider to a chain fork where they own a token, even when they may have transferred that token on the main net.

Again, we plan to implement a degree of 'main-chain' verification to make this difficult or cumbersome for an attacker to do. But forks are always a risk.

This attack could be mitigated by hosting your own Ethereum node and requiring pinning in your client app. However, the tradeoff here is by requiring the user to hit your server the user has reduced privacy and availability.


  • Q: Is there a fee to use these contracts?

  • A: No. This software is free to use and there are no "rents" extracted that go back to the Dotlicense team. (Of course, if you use the contracts, Ethereum transactions have fees.)

  • Q: Why must the client-software hold the private-key ownership of the tokens? Wouldn't it be better for the token to specify the 'allowed client' but restrict transfer to user-held key? This way a user could hold their license-tokens in e.g. a hardware wallet

  • A: If the user held the ownership private key independently, they could freely share a license key with no consequences. When the client application requires the private key, then there is incentive to keep it private (because otherwise the license may be stolen.)

  • Q: Why are these NFTs and not ERC20 fungible tokens?

  • A: Because each individual license has it's own attributes. These tokens are somewhat of a hybrid in that you may sell multiple copies of the same feature. However, the tokens aren't fully fungible either -- they each hold unique attributes.

  • Q: Do I have to pay affiliates?

  • A: No. Affiliates have a baseline rate, which can be zero. Individual affiliates can be whitelisted

Configuring and deploying

(Coming soon)

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Originally created by Dotta for Dottabot




ERC721-based Software Licensing Framework






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