This is both a legal and a breedng question I guess. Legal, because as far as I know these fish are patented, so no one can breed them without a license from the patent holder. Of course Glofish are zebra danios so there is a 100% chance they will spawn in all but the worst of conditions and if there are plants or some kind of hiding places in the aquarium, zebra fry are almost inevitable.
The breeding part is that I do see zebra danios that are claimed by their owners to be Glofish offspring, but most don't look a bit like them and resemble normal non-transgenic zebra danios, while a few may show a trace of the red color, but not nearly as intense or as spread as the glowfish that were initially marketed in local fish stores. Do Glofish breed true? Is the red dominant or recessive, or does it take a more complex turn, such as albinism in oscars which displays a gradient from fully pigmented to fully albino?