1)
Strictly-speaking, DRM (stands for "Digital Rights Management") is technology to make software (games, etc) or data (music, videos, etc) simply not work without first having to first having to ask permission from from an agent of the whoever runs the DRM scheme (this agent may be trusted hardware, such as a Zune or the old iPod devices, or a DRM server run by SecuROM or Valve or whoever).
Loosely-speaking, DRM can refer to any kind of technical protection measure (TPM) intended to control who may use the software or media (although in my personal opinion this synecdochical usage of the term is too loose and it's less ambiguous to use the term TPM).
Ultimately the function of DRM is to allow sellers to be able to deliver software or media "on a tether" so that they can give it to your customers but also retain the ability to take it away from them later if they decide to.
DRM is mostly claimed to be for combatting piracy - however, the software tends to get pirated anyway so it's widely-surmised that it's actually intended as a surreptitious means to combat second-hand sales.
There are also some more novel applications - Steam's "free weekends" and "family sharing", Green Man's gaming's ability to selll your game back for store credit, and the Playstation Network's complimentary games for subscribers all work by using DRM, so it's not always a bad thing. Just make sure that you know what you're getting into and if the drawbacks are acceptable to you.
2)
Yes, GOG is completely DRM-free. The closest thing to DRM that you'll find here (and very rarely, at that) is a CD key. For example, if you get Unreal Tournament 2004 from GOG you also get a CD key for in case you want to play on a server which happens to demand CD keys.
3) "How do Steam, Desura and other sites work?"
- Do you have to be online to play?
For Desura, most games don't require Internet at all, but there are exceptions.
For Steam it's a mixed bag. Most games seem to use Steam authentication as a makeshift DRM scheme, and so you'll need to be logged into a Steam account through the Steam client (and the game must be licensed to that account) or the game will not run, but if you're very lucky Steam's notorious Offline Mode might work and you may be able to play despite not being connected to the Internet. Some games on Steam don't use DRM at all, and you can always run them (although you'll have to hunt through your hard drive to launch them manually whenever Offline Mode isn't working). And some Steam games use additional DRM, such as SecuROM, GFWL, or Valve's on CEG, so there's no single answer that holds for all Steam games.
- Do you have limited downloads?
No, Desura and Steam are both unlimited in this regard.
- Do they check your IP address?
On Steam some games are region-restricted. It prevents you from buying those if your IP address is from the wrong region. It also prevents you from playing games if you are in the wrong region. I don't cross regions often so I don't know the specific rules. But Steam doesn't associate your account with any particular IP address so you can safely access your account from any number of addresses. They do track which region you use to play and buy your games to crack down on people using VPN to buy from regions with better prices.
Desura doesn't care about your IP address, and doesn't even have region restrictions. You may notice that their store pages displays prices in your local currency. I don't believe they track your IP, but they probably use your IP to determine which currency to display.
- What else may they be able to collect?
Steam tracks the hours you play a game, and if you enable their hardware survey it reports the hardware on your machine so that game developers can look at to make sure that their minimum requirements aren't too hight for most of their target audience. Desura doesn't do any data collection at all that I know of. Neither of them are known to spy on you.
- Greenmangaming has a "capsule" to install to play their game - what does it do?
It's for downloading/installing and launching games bought from GMG (except for the ones sold as keys for other services). The idea is that when you're finished playing a game you can sell it back to GMG for store credit. Capsule games use SecuROM DRM to ensure that you can't continue playing a game after you sold it back to GMG.
Post edited February 02, 2014 by Barefoot_Monkey