This plugin has been deprecated and will no longer work after April 30th, 2018. This plugin previously allowed merchants to accept Bitcoin on your Magento1-powered website with Coinbase legacy merchant tools.
Coinbase Commerce is a new merchant payment processor that allows you to accept multiple cryptocurrencies. A Magento2 plugin for Coinbase Commerce will be released in Q2 2018 using the Coinbase Commerce API.
Archived plugin here: https://github.com/coinbase/coinbase-magento/blob/master/archive.zip