Back when Tribes 1 was release for free, VU Games also released Tribes 2 for free. The problem was that Tribes 2 used an account system (because the game featured in-game mail, registered clans, forums, ect), and you needed a valid CD Key to create an account. So they gave out keys for free for a while, but when they “ran out”, that was it.
However, TribesNext is a patched (or cracked?) version of the game that has its own account system and master server list (since VU Games recently shut down the master server). The legality of the whole thing is a little bit suspect, but based on how they killed Tribes: Vengeance I doubt they care enough about the franchise to do anything about it (they wouldn’t even spend the money to release a patch that was already finished).
Want to see some of Tribes 2 before you download? You can view two matches as well as a trailer below: