Do i need the full game to add the content to gmod?

[Pardalis]

Just asking, as i can't buy the games (i only have gmod and hl2) can i download, say, the Portal demo and take the demo-included files to gmod? same with other demo games?
Also a friend bought teh TF2 in a musimundo, can he get the files to gmod? How?

[Divran]

You need the full game.