There were also a couple of (heavily hacked) sci-fi mods--the ones by Harri Polsa about Jade come to mind. All the SHUA mods technically count as sci-fi. Generally people who wanted to do sci-fi in FRUA tended to make their own hacks (change arrows to bullets and bows to guns, put robots as monsters) rather than try to copy BR, which as ProphetSword says above relied heavily on a skill system there would be no way to replicate.
TBH Buck Rogers, as ProphetSword also says, never got much of a fanbase. The setting was interesting--biopunk before they called it that--but they kept trying to sell it as space opera, and they didn't have the popularity of Star Wars, Star Trek, or (1980s) Battlestar: Galactica; the Buck Rogers franchise had pretty much petered out at that point. The only reason the game ever existed was because it made money for Lorraine Williams, who owned the IP.
I enjoyed the games when I finally played them, but I think that was more because of the tactical goldbox engine than anything else, and that point I was thinking of doing a partial FRUA conversion so it was more "can I turn Fireball into that? can I turn Ice Storm into that?" A bunch of people beat me to it, though, and I decided to aim small.
They've always remained more of a minority taste, I think, because the skill system doesn't allow for the sort of tactically complex play the combat system does, and the combat system just doesn't allow for that many types of characters without magic. You've got warriors, who fight, medics, who you hide so they can heal the party afterward, and rocketjocks, engineers, and rogues, who fight...not as well and have different skills you use at various points in the game. Hacking a computer is a simple roll, so you just save and reload...there isn't 'let me use this software for this electronic intrusion countermeasures' like in, say, Neuromancer. Everyone can use every item, so there isn't the whole set of tradeoffs like 'fight durability versus magical firepower' or 'advancement speed versus versatility' that characterized the AD&D goldbox engine games. Playing Pool of Radiance with three fighters, a cleric, a thief, and a mage is a very different experience from playing with a fighter/thief and five cleric/fighter/mages (or one cleric/fighter/mage
). Buck Rogers....you can see how far you can push a lack of non-warrior non-medics and that's about it.