Can i use the free source game i have for garrys mod?

The free source game i have is Hl2 dm from the ati offer. I installed it. Can i install/play garrys mod using that?

Notice: This game requires that you own a Source engine game such as Counter-Strike: Source, Half-Life 2, or Day of Defeat: Source. Click herefor a full list of games that meet this requirement. Please note that Portal: First Slice and the bundled Half-Life 2: Deathmatch do not fulfill this requirement.

Just got FUCKED up the ass.

Funny, the free full game of Portal doesn’t count either.