fisk0: Steam in itself isn't DRM, but it has DRM functionality that is utilized by many games. I think Static had a lot of points which you didn't really address.
Once Steam has downloaded a game, it is on your computer, and if the game does not use any third party DRM or is one of those that checks Steam for authentication (which are not every game on Steam - mostly it's the Valve and Steamworks titles, but obviously many other games - still, not all of them), you can copy the game folder to any computer or run the game without Steam.
Steam doesn't give you an installer in most cases though (at times there is a subfolder in the game folder containing all the things that you need to install to get the game working), so those games that require changes to the registry or installing of various codecs and system files are going to be harder to get running, and will require a lot of manual copying of files to their right locations and registry editing - but it's certainly not impossible or something that you'd need to use third party cracks or something to fix.
Almost all the old classics on Steam use a standard Dosbox setup, with no DRM whatsoever, many indie title don't use any DRM either.
The only thing Steam does in those cases is to obscure the location of your game files, but they can easily be found and copied, just go to where you installed steam (usually c:\program files (x86)\steam, and then go to the \steamapps\common subfolder and you'll see the folders for all the games you have installed, in many cases you won't have to do anything but to copy those game folders to another computer and run the game executable within, very few of the games made before 2005 or so check for a running Steam client and will happily start without any trace of Steam on the computer.
In many cases this isn't too different from how GOG works - once you've got the game downloaded you can do whatever you want with it, if the service suddenly shuts down without you having the files - you're screwed.
The people behind Steam have on multiple occasions said that Steam wouldn't just suddenly seize to exist, they say the would give advance warning and unlock the games that require steam authentication to run.
We obviously only have their word on that, there's no mention of that in the TOS.
I've actually never come across a game that hasn't had the steam drm wrapper on it's executable. Even alot of the dosbox games you mentioned earlier are suspect. Whenever I attempt to run a game distributed through steam, it crashes complaining about not being able to find steam if you don't have it running. There was a big debacle about that a few years back where steam was adding their drm wrapper to a dosbox executable and some people thought this was going against the gpl license that dosbox had (long story short... they added the gpl license into a text file in the folder and everyone was happy)
I have to admit I've heard of some indie games not having the steam drm on them, but never figured out which ones they were. Do you know of any games that actually lack the steam drm even when distributed through their service? I'm curious now.
I think the number titles out there on steam that don't use their drm is almost nil.
