They don't do any actual display resizing under any circumstance. Instead, they display to the full resolution of your primary display in what I'm assuming is a fullscreen, borderless window. If you set a lower-than-native resolution, they still output full resolution but with a smaller frame buffer and scale it up. It makes switching applications absolutely seamless and minimizing and restoring as instant as any windowed app.
Thanks for explaining SDL2. Now I know, why some steam games don't destroy my desktop by changing resolution. This is really awesome.But doesn't that harm performance?
On topic: Great to see new (=old) games ported to linux. Sure, they're old. But i like, because so you don't have to build up a "linux game collection" if you previously had a "windows game collection". (i hope you understand, what i mean)
Portal and Dota2 are my favourites, but as i read Dota2 for example uses a special version of the source enging, which needs some extra porting.
Steam isn't really a strong DRM. It's dead-easy to bypass. I'm not gonna mention here how, but you can install Steam, download the games and play them without paying (offline, since most online games have the DRM on the servers and they check your account when you connect.) But many single player games can be illegally downloaded like that.
Steam is really not some form of intrusive DRM. It's mostly comparable to the old days of games having a simple CD-check. If you're looking for DRM methods that trully deserve to be boycotted, you should really look elsewhere (hint: EA with the malware they install before you can play BF3.)
You would be surprised with amount of people that plays old games...not to mention the emulation of much much older systems...there are people that likes to play Sinclair ZX Spectrum games....way way older than 10 year old PC games.
Those older Valve tittles are excellent for older or not so powerful rigs....i bet that they play nice in regular HTPCs.