I think you can use portal in gmod 10, but I'm not so sure.
No it is not. It requires one of the games in the half life 2 series such as TF2 portal or half life 2.
No. Gmod is only for PC
no. gmod is only for the pc.
You need to download Gmod 9.0.4c when you start there will be 3 choose unmark the Gmod 9.0.4b and your set to go and play gmod 9 online.
Gmod 10 is a pay game. It can be purchased from the Steam store at http://store.steampowered.com It costs $10
you click the shortcut icon er the gmod .exe/file!
Any Source GamePreferably CS:S as most gmod users have this
gmod 9, yes gmod 10-no
piggymoo.com has all of stargate, but I'm not sure what gmod is.
go to steam.com here are some links related to Gmod to help you: Steam: http://store.steampowered.com/ Download stuff to Gmod here: http://www.garrysmod.org/downloads/ About Gmod: http://www.garrysmod.com/about/ Gmod fourums: http://www.facepunchstudios.com/