You are accessing paid content without paying for it. Even if Tripwire no longer actively develops KF1, the DLC remains copyrighted commercial assets. Using an unlocker violates the Steam Subscriber Agreement (Section 3.C: "You agree not to... modify or cause to be modified any files that are a part of the Game").
If you truly love Killing Floor , do the right thing: buy the Complete Pack, support a developer that gave us moddable dedicated servers, and enjoy your golden chicken suit without the risk of a cryptominer hidden in a DLCFix.exe . killing floor 1 dlc unlocker
The unlocker fails. Expect red text in the console: "DLC validation failed – Kicking player" (soft kick to spectator mode). The Legality & Ethics: Is it Piracy? This is the gray area. You are accessing paid content without paying for it