I was wanting to use either raknet, enet or sdl net for my game im making. What I was wondering, is, if I use one of these free things, can I still charge for my game? And which one might be better for a real time space game? Thanks

I found this one extremely easy to use
http://enet.cubik.org/

But if you want a really good 'professional' one that's a little harder to code, try this one
http://www.rakkarsoft.com/