The install directory for Postal: Brain Damaged seems to contain a folder named "POSTAL Brain Damaged_BackUpThisFolder_ButDontShipItWithYourGame" lol. It contains some DLLs, unity debug databases and loads of C++ source files in there.

The Steam version does NOT contain this folder. So what's this all about. Did someone accidentally leave the source code in the game package by any chance?

Looks like the latest patch has removed this folder now.