I don't know if anyone is familiar with Star Fleet Battles, but it was mostly based on the Tech manual and had no agreement with Paramount until much later. The creator of the game actually got the license from Franz Joseph.
I'm sure if Gene thought he could squeeze any money out of it, he would have demanded it, as is his right for intellectual property.
Gene was the person who inserted the IDIC into ITITNB so he could sell them through his Lincoln Enterprises.
BTW, I found the Tech manual in the library and borrowed it and poured over it. I loved it. I didn't even know it existed before that. I think the canon status is irrelevant as most things don't have any consistency between them, so I just enjoy what I like and don't worry about the rest.