Wasn't it the last ruling in the court that gamesas was correct in distributing the Fallout series repackaged as one game? If this is true, then gamesas still owns the copyright and thus other rights like music rights to the original Fallout games.
gamesas only owns the distribution rights for the previous Fallout games in their present form. This means they cannot port the games to different platforms, update them in anyway, etc without permission from Bethesda.
You're the one who wanted to use Fallout: Tactics music for that video right? If that's the case, simply contact ZeniMax Media since all roads lead to them anyway.
Mark Morgan did not compose the music to Fallout Tactics, Inon Zur did. Furthermore, it is not the composer that owns the rights to the music, it is the game's publisher.