Risa

There's a lot of fighting between DS9 and B5. The story goes that B5 series creator J. Michael Straczynski had shopped the series bible around, including to Paramount. They weren't interested, but when they heard it got picked up by WB, they rushed their own space station based Star Trek series forward. With people coming over from TNG, they get a pilot ready faster than JMS can create a series from scratch.

Since they had the B5 series bible, there's long been allegations that DS9 is a ripoff of B5. Indeed, there do seem to be some elements stolen out of it. For example, the pilot of B5 has a "changeling net" technology that lets people impersonate each other, which had apparently evolved out of an early draft of a changeling species, which DS9 copies outright.

What Paramount studio execs did was definitely underhanded. They were deliberately pushing out a show to make sure B5 wouldn't get to the same level of popularity as Star Trek. They probably did steal elements from the B5 bible and pushed Berman and Piller to use them.

However, fans make more of the similarities than are really there. Berman and Piller were almost certainly unaware of why the studio was pushing certain ideas and where they got them from (and JMS said as much at the time). Most of the stolen elements are ultimately superficial. The way the central conflict unfolds is very different, the characters are very different, and the technology is all different. B5 doesn't center around a planet coming out of a long term colonial authoritarian government, and DS9 doesn't have humanity crawling out of a war that nearly destroyed it and which ended for mysterious reasons. B5 doesn't have an excellent father-son relationship, and DS9 doesn't have a wisecracking ambassador who's very likeable despite doing some incredibly fucked up things.

They are both excellent shows, and well worth your time.