Is it possible to play Prop Hunt in GMod without CS:S?

Solution 1:

Yes, you can (even CS:S maps)!

Downloading the appropriate files from here ^{(click on 'Garry Content')} as shown in this video will work ^{(He'll show you where to place the files)}.

It's just textures (and maps, if you need it) for use as an addon to Garry's Mod.

This is completely legal because there is another [more complicated] method listed on the officially affiliated site which not only details in its FAQ why it's legal, but it uses SteamCMD (an official tool from Valve) with the login of anonymous (a free account) to get the files.

Solution 2:

It depends. If the server is running a CS:S map, you probably won't be able to join. (I have CS:S so I can't say for sure) If they are running a map not prefixed for CS:S (de_, cs_, etc.) then you should be fine. However I have friends who have Gmod without CS:S, and they're reported issues. In playing a lot of Gmod gamemodes such as TTT or PH, they will be missing textures used by mapmakers from CS:S to make the map. This results in the map having a lot of missing texture errors and everything appearing as purple and black checkerboard on their screen.