In my attempt to keep such a hidden gem alive, I will post patches and other critical files here.
2017–03–12 SWAT4 Dedicated/Multiplayer Patch GOG took SWAT 4 under it's belt, and released a "new" version. I recently purchased the GOG version and found that just like the old CD version, game server listings didn't work. Someone created a patch and alternative servers to fix this issue. This works great and all, but if you run a server you will get a message of "Invalid CD Key". Running a dedicated server will give ServerCDKeyAuthenticationFailed and crash when someone connects to said server. You can blame whoever owns this alternative server for not putting into place a "validation" component. Download Mirror Download (MediaFire)