If you find yourself "unable to shade polygon normals", then you're a dirty pirate. The error code includes the users' Steam ID so Garry can banish the jolly rogers.
"Just enabled this error in GMod today. It happens when you pirated it. Having fun watching people complain," Newman. The official Garry's Mod forums have lit up, as has Google, with people looking how to fix this error troubling their pilfered copy.
Garry's Mod is essential a physics sandbox for users to play around in, and it started out as a Half-Life 2 mod. The $10 box-of-fun now supports most Source-powered titles from Valve allowing fans to mess around to their hearts content.
Should more developers get creative like this to weed out the leeches?