Is twitter trying to claim ownership over bootstrap? I assume you 2 guys left twitter to do this as-a-living. The post reads like a "Twitter does not own this, we made it on our own time, Its just the two of us, etc. etc."

Do you even need to worry about this? Pretty sure since its open source you guys are fine, unless something in your twitter employment contract says otherwise. That being said, Bootstrap is a valuable asset to the web and I think you would be not-paranoid in assuming that twitter might want to call it a asset it owns.

Step 1 for you guys should really be moving from http://twitter.github.com/bootstrap/ to http://domainyouownpersonally.com