Wow roboman do you not understand copyright? We would be issued cease and desist letters if we made a clone "RA3" game in the quake3 engine. Everything concerning "robot arena" is ATARI's intellectual property, you can't use it for whatever the
you want...
We could use the quake3 engine to make a robot arena-type game and call it something like "DSL" with no robot arena attached, but that would still take a ridiculous amount of effort... and it also wouldn't cost any money or require the rights to the game, which is the opposite of what this thread suggests we do...
If anyone wanted to make a new version of this game using a open source engine would be the best idea. Quake 3 engine might be good - im not a coder i have no idea but its definitely better than buying the RA2 game.
You dont have to call the game RA3 and even if you do i doubt anything will happen. Robot Fights, Arena Of Robots, Robotic Arena. Any stupid name will work.
Selling it is not viable. Modders have a inherent problem that they lose interest and arent real coders. Unless you make a real company and hire people you wont be able to finish or sell it.