So I'm wondering if the multiplayer will work with this version from GoG? I don't see anyone talking about it. I'm gonna tell 3 other buds to pick it up but just want to make sure we can all play online together even if only via Hamachi.
Any of you guys playing multiplayer??

As far as I can tell, multiplayer works, but no one seems to be playing.

I explained this is another thread, but I'll post it here too in case you didn't read that one.
I can't say for sure as I've not re-installed the game to look, but I can only immagine that PXO (Volition's/Parralax's online multiplayer service and master server) are down and no longer functioning. If that is the case, you won't be able to play online and get medals and ranks, etc. If you want to do multiplayer you'll probably have to do a lan game with friends. If you can't do a lan game in the same room, use Hamachi, it is a nice program that lets you play a "lan" game over the internet. If none of your friends play FS 1/2, you can always find people on here and add them as a friend on Xfire or something so that you can all hook up and play. Just my thoughts :)
You can get Hamachi here: https://secure.logmein.com/products/hamachi/download.asp

you can always download freespace open and try to set up a game on that, i forgets the download link, but google is your best friend.

Not sure on the online MP. but some friends of mine played it MP on a local lan for 8hrs and it was a blast. If the online thing didn't work you could always just use something like hamachi and use vpn tunnels to setup a mini lan over the internet and that should work as well.

theres actually an online server thats been put up thats been around for a few years. i havent had a chance to try it out yet, but its hosted on gamewarden
link is here: fs2netd.game-warden.com

I'd also recommend to monitor these IRC channels:
#hard-light
#MULTI

Is the multiplayer only vs or is there Co-Op?

There's cooperative, free-for-all, and team vs. team.