Darrin Drader
Explorer
and for what it is worth, at the very bottom edge of the Star Frontiersman | Magazine! page is a piece of text where it is stated that he has limited permission although it does not directly define these permissions. See last few words of this line.
You know, I'm surprised that nobody has brought up the core book remasters that are up at Star Frontiersman. Digitally Remastered | Star Frontiersman
If I were so inclined to run a Star Frontiers game in the near future, I'd be looking to these instead of the classic game.