deja65: I would advise you to contact GOG through their support channels. They should be able to include the mentioned language version if the licencing allows it. It sadly mostly depends on the publisher and not GOG. Cheers
AllenFreemanSP: That means it depends on Activision and then with Microsoft, but it seems like bullshit it's not garanteed to tell about that copy and there would be like so many copies of SWAT 3 despite it could be in a "Computer Hoy Juegos" CD and it has its voice acting credits somewhere. Thank you anyways.
The problem is that for certain languages or even OS versions, sometimes the publisher is completely different. For example, XIII from Ubisoft, for which we have the Windows version on GOG but not the macOS version, which was published by Feral Interactive. I think there shouldn't be any licencing/copyright issues with the spanish version of SWAT 3, but Activision got bought by Microsoft, and they don't care at all for GOG. I would go as far as to say that the Activision games here are at a substantial risk of being removed at some point, but I hope not :) Cheers