If you are thinking that this won't have any effect in the long run, allow me to politely disagree. In my country, every 11-year-old child recently acquired a free netbook with Ubuntu pre-installed (on most of them at least). Pretty much each one of those lads (and ladies) I have spoken with likes Ubuntu more than their WinXP installations - and pretty much all of them run WinXP anyway, because "games don't work on Ubuntu".
Some of them have discovered the Ubuntu Software Center and started installing games from there (I was mightily surprised when I saw my cousin playing bzflag on an impromptu lan party!) but that's still not enough: no Starcraft, no Counterstrike, no Unreal Tournament (all of those run but are far too slow to be playable on Wine - plus, Wine is far too difficult to setup).
My point? Add a few quality games to Ubuntu and people *will* come. That's all.
Debian doesn't matter much, as Ubuntu is currently the flag ship of desktop Linux. As long as it can be legally included in the repos it's an enormous plus. Also, perhaps a few fans could take the code and build a new game using the source (wouldn't personally mind some sort of Aquaria clone, thou keeping the art so classy and stylish could be a real challenge).
They've only released the data from the demo (to be redistributable but not sold) so you will still need to buy the game. I expect the rest of the titles will do something similar.
It really sounds like you need to educate your young Ubuntu users a bit better (or maybe Ubuntu needs to make games easier to install from the software center?), the games that comes with the default WIndows install isn't much better.
There are quite a few best of/top ten etc. lists for Linux games, and I expect also specifically for Ubuntu.
According to the wolfire post on Lugaru,
I haven't downloaded the snapshot (waiting for the repository instead), but this implies that all assets are included, not just the ones in the demo.The game assets are included in the snapshot, and can be redistributed for free, but cannot be resold without our permission.
Edit: also, yeah, but no Linux game can really match Starcraft.
This is certainly great stuff.
The sad part is that the OSS community is better at producing engines than at producing high-quality contents, so this might not be as much of a boost for new OSS games as one might imagine.
Still, it will be great to port the titles to new platforms, fix bugs, improve integration with the OS, add some features, and help users create new levels.