...wait a second. I swear I've heard this before.
Why does everyone who works with voxels act so secretive about how their rendering works?
No one cares.
No one. Cares.
Really. No one is going to steal your clever memory optimizations. They don't care.
If you've done something clever, explain it. Maybe you'll get a hi-5 from someone. Being all, coy about it is just irritating.
The game dev community has a love/hate relationship with open source: on one hand a lot of widely used tools are under open source/free software licenses (box2d, SDL, etc.), but on the other hand you'd be hard pressed to find an indie willing to release his source code (Jason Rohrer I love you).
There's definitely a technical reason for it (game code is often hacky and not that reusable), but I've observed that it has to do more with the sense of pride of the developers ("my code is too ugly people are going to think I am a bad developer").
Or maybe that they just don't want to compete with people building on --or even outright cloning-- their products. Of course, they're perfectly happy building on others' work.
LD48 requires that you open source games in the jam, so that's 1000s of games with available source code, even if most of them don't live on Github. Quite a few Humble Bundle games are open source as a result of the bundle (http://indiegamebundle.wikia.com/wiki/List_of_Humble_Bundle_...) I can think of other indie games that are open source, Stephen Lavelle's games (http://www.increpare.com/), Game Maker Spelunky, Mari0, Infinite Super Mario Bros. Roguelikes are also usually open source.
Libraries or contributions to frameworks that have come from indie game developers include MojoShader (http://icculus.org/cgi-bin/finger/finger.pl?user=icculus&dat...), MonoGame for Mac OS X, Linux and NaCL, (http://supergiantgames.com/index.php/2012/08/bastions-open-s...), Flashpunk and Flixel.
I also think it's unfair to knock game developers for not open sourcing their games. Last time I checked, many startups open source libraries and helper code, but very few of them open source their product code. The indie game community is also much smaller than the startup community and also less technical on average.
It's definitely getting much much better, as you described it - but it still has a long way to go. I do tend to hang out more in very FOSS-centric circles, so maybe my perspective is a bit skewed by this.
(and I do agree with you re:startups - I wish we saw more open source product code. Gittip is doing a great job with that: https://github.com/gittip/www.gittip.com/ )
Yep. I'm sure the majority of them are also GPL violators.
They love to take but never give back.
Since when has "it's nice to share code" turned into "you're probably a criminal if you don't share code".
But one look at today's 'app store' ecosystems and current game dev culture is all the evidence I need. It's a profiteer's paradise.