Acceptable Use Policy
For the most part, the things that you shouldn't do aren't supported by the API. You're welcome to use our code for commercial projects, etc. Please see our license (MIT) for details.
Our use policy is roughly modeled on the PlanetLab Acceptable Use Policy. The main things to know are: (1) no illegal activity, (2) don't try to hack into Seattle user machines (if you want to test a vulnerability, let us know, we have machines set aside for this), and (3) even if the system doesn't have outgoing or incoming IP / port restrictions, don't abuse this. Basically, it boils down to treating the system as though you're a network admin and it's on your network.