Not sure if anyone here has seen us yet .. but Titanium is an open source/open web alternative to AIR that just had it's first Preview Release (PR1) a week ago. We currently support OSX and Windows , and are hard at work refactoring and getting a Linux release into the fold for our PR2 release in January.

We're licensed under ASL and using lots of open source techs (WebKit, Chromium, Gears, libXML, to name a few).. come check us out!
http://github.com/marshall/titanium/tree/master
http://titaniumapp.com/