also if you're looking for free multiplayer online, look no further than subspace/continuum, came out in like 1995 and looks like a souped up Asteroids but the game is an absolute treat.
you can download the game here
and i also recommend playing in the "trenchwars" zone. there are lots of zones with different settings and formats and maps but i find the trenchwars zone to be the most consistently fun. Picture 15 on 15 capture the flag with spaceships, eight different spaceships with their own strengths and weaknesses. that's the public game anyway (capture the flag) but there are all sorts of combat tournaments and events hosted all day long. the graphics aren't modern but they don't need to be, it's playing on the keyboard which i really enjoy, it's "easy" enough to be making plays your first time but you have no idea how much depth to the learning curve there is.
edit- it's not for mac and it's really made for desktops not laptops, but give it a shot