Maybe I'm completely missing a joke (
whoosh me if I am), but assuming it was possible to buy Zap! rights, what content would we get? Anything beside the privilege to protect and sell the game?
I too would love to see Bitfighter on Steam, but as others have undoubtedly pointed out, Bitfighter needs to sell something - even if it's free-to-play - to enjoy Steam market space. I wouldn't be opposed to charging for the game (although one of Bitfighter's primary appeals that drew me in originally was its free price point). If Bitfighter were to cost something, I too think it'd be wiser to charge a little more for the impression of quality. That would also allow for attractive sales during holiday seasons.
There are of course drawbacks - as Wat pointed out, taxes are quite the bear. I would also wonder about responsibility and liability - what happens if the game breaks? I would imagine the devs would be under more pressure to provide a patch faster when $$ is involved. Not to mention potential legal requirements of supplying a complete game to the consumer.
More importantly, I am inclined to discourage people from thinking Steam is a "be-all end-all" solution to our participation problem. Steam acceptance would probably boost activity, but it's not a magic genie. All our problems wouldn't be solved overnight. There simply is no one and done solution for growing Bitfighter. It's a constant, gradual process that might occasionally be helped along by media attention / exposure.
To stray from being a total debbie downer, I would instead encourage people to look at game archiving sites - like GameJolt! - as well as Let's Play video authors and game review blogs. The easiest thing you can do is play the damn game

to encourage newcomers to stay!