Joe's wife worked for Piller at the time. Piller talked about that in an interview back then...
One reason, in fact, that folks at Trek were impatient with the pretense that the B5 people didn't know exactly where DS9 came from.
But then, that bit of info would have screwed up a perfectly good conspiracy theory.
It's hard to say whether the Trek producers were simply incredibly polite in tolerating this whole thing or they simply had better ways to spend their energies than to engage in a stupid pretend controversy on computer bulletin board services. Some of each, I suppose.