It seems to be a full development environment with a python based scripting system.
Free and open source, extensible through C++.
multi platform output
Take a look at there features page yourself, they just had their stable 1.0 release.
I haven't really looked into it yet but sort of reminds me of gamemaker. edit - in features.
Thought it might be useful to post in the beginners forum.
edit2 - they also seem to need volunteers, so take a look it seems like it might be a worthwhile endeavor.