This seems to be the most hot-button issues among the fan-bases of Star Trek and Babylon 5. The simplest answer is often that Deep Space 9 was on the air first, and therefore, the premise of Babylon 5 was pirated from the Trek spin-off. The writers of The Big Bang Theory seem to operate under that assumption. Sheldon Cooper’s dislike of B5 is a reflection of a panel of writers having seen the series and not “getting it”. Sheldon had even gone as far as to call the series “hopelessly derivative.” In Sheldon’s defense, though, some aspects of B5 came from the Lord of the Rings franchise, such as Rangers keeping an eye out for a returning darkness and the planet Z’ha’dum being based on a place called Khazad-dum.
Taking note of the lessons of mainstream television, which brought stories to a centralized location such as a hospital, police station, or law office, he decided that instead of “[going] in search of new worlds, building them anew each week”, a fixed space station setting would keep costs at a reasonable level.
In fact, according to JMS, he pitched his idea to Paramount back in 1989. That idea would later become Star Trek: Deep Space Nine, while JMS’s idea would became a Warner Brothers TV series a month after DS9’s first airing. Suffice to say, JMS was an innovator in every sense of the word. Babylon 5 was one of the first TV series to contain an ongoing story-arc, a concept he had brought to the short-lived sci-fi series Captain Power and the Soldiers of the Future, which also depicted a greater reliance on CGI that B5 is known for.
The Babylon 5 television series centered around a more “realistic” view of the future where all the problems of crime, poverty, and prejudice haven’t been solved with more “realistic technology”—jump gates that open portals into hyperspace as opposed to warp drive and starships with rotating sections that create gravity rather than an artificial gravity field. While Deep Space Nine does largely keep to the Trek precepts in terms of a more utopian humanity, it carries the warning that it could all be washed away more quickly than one might think because of war and politicians in high places making a few compromises. Groups like the Maquis and Section 31 drive home the point that it is “easy to be a saint in paradise.” We see throughout the series that our heroes live in less than idealistic times and must play fast and loose with the rules from time to time.
So, yes, Deep Space Nine was derived from Babylon 5 more than the other way around. The question now becomes, is that necessarily a bad thing? I say no simply because ideas are not conceived in a vacuum. Additions to scientific knowledge happen largely because of scientists refining and correcting the ideas and theories of their predecessors. Sheldon may needle Leonard for not having done any “original research”, but replicating the research of earlier scientists is the very definition of science’s self-correcting mechanism.
And with that in mind, ideas in the creative arts are refined and improved from those of their predecessors. The original Star Trek series itself was in some ways a Western-themed TV series in outer space at a time when Bonanza and other Western-themed TV series were big hits. It was rife with allegories to highly relevant political and cultural phenomena from the Cold War to the hippies. Just about any work of fiction is based on ideas and events that existed long before that work of fiction. Various elements of George R.R. Martin’s novel series were based on real-life historical occurrences, in addition to the War of the Five Kings being largely based on the Wars of the Roses.
I could go on forever with this, but my point is that one TV series was derived, rather than stolen from the other. JMS had observed that good writers borrow and great writers steal. I have followed this philosophy with my fan fiction writing by incorporating what made B5 better than Trek and incorporating that back into Trek fanon.