Two excerpts from JMS's commentary in the book Babylon 5: The Scripts of J. Michael Straczynski, Volume 1:
For the five years it took to make and sell Babylon 5, Star Trek was the bane of our existence, the constant stumbling block we had to overcome in nearly every meeting. We were told, repeatedly and enthusiastically, that there was no market for any SF series other than Star Trek. Their logic was as shortsighted as it was absolutely unassailable.
Ironically, one of the places that did understand what we were doing was Paramount Television, which made overtures to us about picking up the project after reading the spec movie and the series bible and treatment...only to suddenly change their minds at the last moment, no explanation given.
We pick up the next part of the story with an excerpt from the Babylon Podcast interview with JMS in the book Encounters with J. Michael Straczynski:
We almost didn't get there because after we shot the pilot, I got a call from Walter Koenig—who played Chekov on Star Trek [and who would later play Bester on Babylon 5]—who was having lunch with a guy at Paramount. He said, "I wanted you to know they're doing a show based on a space station [Star Trek: Deep Space Nine], a diplomatic outpost, jumpgate [wormhole, in Trek lingo] nearby, commander with a sort of a mystical history and destiny [Benjamin Sisko], female second in command [Kira Nerys] and a changeling [Odo], which you have in your movie. They're trying to subvert what you're doing and co-opt it."
At that time, Warners and Paramount were doing different competing networks. They figured, "We can take what they're doing at Babylon 5 and co-opt it, and we can sell it and kill their show." They were actually telling stations, "If you buy Babylon 5, you can't have Deep Space Nine." They tried to sink us wherever they possibly could. "They're gonna look like crap," they told people, "Babylon 5's gonna look cheap and terrible." They did everything they possibly could to stop us. It was trench warfare for a long time and they almost sank our ship.
I think, more pissed off than anything else, Warners decided to go ahead with it. It was a pretty obvious riff on our show. In fact, one of the cast members found Peter Jurasik—who played Londo on our show—at a party, pulled him aside and said, "I want you to know, all of us on DS9 know that our show came from your show, and on behalf of the cast, good luck." Which said a lot.
I wanted to sue their asses off, but Warners said, "If we sue them, they'll countersue us. Both shows could be lost in litigation, and you'll never get your opportunity." So I bit the bullet and didn't take action. Warners owned the show at that point, so we had to sort of sit back and watch them trying to eat our lunch every week.
An excerpt from a post to GEnie by Straczynski on 29 September 1992 published in the book Asked & Answered, Part 3 presents a summary of some of the similarities between the Babylon 5 pilot and the Deep Space Nine pilot:
If it were only a matter of set design, you wouldn't hear a peep from me. For what I hope will be the last time, here's how it lays down:
|BABYLON 5||DEEP SPACE 9|
|Commander Sinclair||Commander Sisko|
|Female second in command||Female second in command|
|Shapechanger in original script||Shapechanger in pilot script|
|Located near a jump-point (warp)||Located near wormhole (warp)|
|Number-designated space station||Number-designated space station|
|Similar prosthetics||Similar prosthetics|
|Similar sets||Similar sets|
|Female 2nd fending off attack at end||Female 2nd fending off attack|
|Cmdr. haunted by recent war||Cmdr. haunted by recent battle|
|Cmdr. is unmarried||Cmdr. is (now) unmarried|
|Freeport/port of call||Freeport/port of call|