Tolar created the program, and spent some time on it. Apparently, Sisko was not satisfied with the first version created, and Tolar had to go back and make a few slight modificationa.
There's no indication that someone else made it. Tolar is the specially skilled holographer/holoprogrammer.
I'm curious why we're calling him "a bad person." We know almost nothing about him. He got in a bar fight, yes. Other than that, all we know is that he's associated with Garak(but fears Garak), and that later, Garak refers to him as 'one criminal.'
So I guess he's a holoprogrammer willing to create forgeries, and at one point did something to warrant ending up in a Klingon prison, which could literally be anything. Perhaps he got too close to a Klingon border.