.x files can never be re-distributed nor can the original texture file.. I don't see why .fpe files and any accompanying texture map files such as "N" and "S" couldn't be given away for others to use who
already own or who will be buying those model packs. After all you would only be able to use them if you already have the .x file and original texture file. That means you would need to purchase the model pack or model if available in the store before it can be used.
I suppose, you still may want to get permission from the artist.

I'm addicted to programming and coffee!