None of the Humble Bundles actually include the source code with the purchase. Sometimes the publisher has released the code of the games included in the bundle on their own outside of the actions of the Humble Bundle.
The reason that Jack Claw in this bundle was open sourced is because it is a prototype.
You can find sourcecode for games included in other versions linked from Wolfire's blog:
It's an interesting free-form (ie, no true paths) tower-defense game. Pretty large tech tree, pretty long game, pretty hard, and it under-went a major gameplay-overhaul not too long ago. I'm not convinced it's better, but it did noticeably simplify a few things which were over-complicated. And large changes / updates are generally indicative of developers who listen. As is the overall level of polish, which I'd call abnormally high.
Definitely worth a try, unless you dislike tower defense games.
It is awesome... They did make a lot of changes (like 12 or so new versions since then) so you should fetch the latest when you are ready to give it a try. The whole gameplay is different, basically they released a "pretty good" game for the bundle #2, then iterated with feedback to get to "awesome". Got to admire this attitude.
Also played their Droid Assault, sell it on their site in a bundle as well. It's an instant hit, could hardly stop playing, just love it :)
http://www.puppygames.net/droid-assault/
The reason that Jack Claw in this bundle was open sourced is because it is a prototype.
You can find sourcecode for games included in other versions linked from Wolfire's blog:
http://blog.wolfire.com/2010/06/Aquaria-goes-open-source http://crypticsea.blogspot.com/2010/05/gish-open-source.html http://blog.wolfire.com/2010/05/Lugaru-goes-open-source http://frictionalgames.blogspot.com/2010/05/penumbra-overtur...
As far as I know, the second Humble Bundle did not include any games of which was later open sourced.