Never heard of it. And I don’t read the comics. Was he trying to link Spider-Man into the Babylon 5 universe?
Whaaaaaa? No, of course not. Just because he created Babylon 5 doesn't mean that's the only thing he's capable of writing (and since it was a Warner Bros. franchise, it would be more likely to cross over with DC than Marvel). Straczynski was the regular writer on The Amazing Spider-Man from 2001-07. Morlun was the villain in his debut storyline on the series and a recurring adversary in subsequent years.
And why does it matter whether you read the comics? Most of the characters in any Spider-Man novel are going to be from the comics -- that's a given to start with. Spidey, Mary Jane, the Black Cat, the Rhino, they all came from the comics the same as Morlun, just earlier.