gameon: Now thats ideal! Would be great for any torunaments here on GOG.com. If its easy to configure/use that is....
It's easy as fuck to use.
You install it, run it, choose a name (I believe it autofills it in based on the user name of your PC, but you can just delete and replace with whatever), then one person will make a network naming it GOG or whatever, then add a password. Everyone else then just joins existing network, types GOG and the pass and connects. (Edit: To join a game) you copy the iPv4 IP (right clicking on person's name in the network) and paste that to direct connect to an IP via it. If it does a direct connect. Never tried it for a game without a direct connect like that.
However, I don't know how large the networks can be. Checking out the one my friend made (for free) it allows 5 people in. And the people signed in count even when not online (people would have to leave the network before closing down hamachi to make room for others). According to the site it is $29 (currently on sale for 19) a year for a network up to 32 people. Might be better (aka cheaper) to have some meeting ground to organize games and from their people could make their own hamachi networks for free. Granted that would only work for 5 people or less to a network. The only thing that would be lost from doing it that way would be the chat that you can do over hamachi, that would have to take place at the meeting ground (and obviously people in-game would talk via that).
And I see no way that this would be illegal, it seems to be similar to the GOG group on Steam. Some unofficial meeting place for GOG users.