Obviously the fictional use of the very specific phrase "USS Enterprise" is copyrighted by Paramount, and no other show can use it. That's not in question. But what if it's something else? Babylon 5, for example, has all its ships (Earth ones, anyway) marked with EAS. So if B5 had somehow wanted to introduce an EAS Enterprise, they could have done that, right? EAS isn't USS. Nor is USAF, which as I understand it is what the Earth ships in Stargate SG-1 use (since they are all operated by the Air Force). But there is one line in SG-1 when somebody says "Sir, we can't call it the Enterprise". So why not? Does this only apply to the show's own "universe"? The copyright involves only the term USS Enterprise, isn't that right? So given this, I don't see how B5 could have been kept from having an EAS Enterprise, or SG-1 having a USAF Enterprise, or, hell, Firefly with an IAV Enterprise. About the only thing I can think of is that even if those shows COULD have done it, they deliberately chose not to, so as to avoid stepping on Trek's proverbial toes (although since FF actually went out of its way TO do that, I'd half expected them to actually HAVE an IAV Enterprise just to stick it to the Trekkies). Makes sense, doesn't it?