Use the workshop_download_item command, specifying the of the game the mod belongs to and the Item ID you just copied.
This is the most reliable "official" way to download Workshop content without the standard Steam client. Download SteamCMD : Get the latest version from the Valve Developer Wiki Extract and Run : Place the in a dedicated folder and run it to update. : In the command prompt, type login anonymous how to download free steam workshop mods without game
Use SteamCMD for reliability and safety. It takes 10 minutes to learn, and once you write the command down, you can download any public mod forever. Use the workshop_download_item command