For the past year, I've been working on a game achievement system. I didn't like the way Steam is taking over and there is no solution for open source software. My solution is currently an addon to Hubzilla although I may make a standalone server soon. Details can be found at:
http://identicalsoftware.com/gamerzilla/
My achievements can currently be seen at:
https://social.freegamedev.net/gamerzilla/dulsi
I do plan on adding support to Bt Builder at some point.