Bungie released Marathon for free as well (including all assets and code).
http://www.eurogamer.net/articles/2014-05-12-bungie-to-updat...
(disclaimer: I work for Bungie, but not on that project)
Soon after the GameSpy services shut down, he wrote an emulator to replace the official master server. Bungie then (shockingly) released v1.10 to point the game to the new server, and stepped in and ate the cost of the AWS services used to power the lobby.
Source: I gave my life to that game for a very, very long time and still check in on the community every now and then.
Fun fact: Eric Koger, the CEO of ModCloth.com, also spent quite a bit of time reloading his pistol and rifle.
From a historic perspective, the untouched release version of all games would be very interesting.
Not wanting to downplay the release, though, it's very kind.
While I say "original", these are different from the retail versions of the original games, which required serial numbers. Bungie's Jason Jones removed the serial number check himself, without the original source.