I don't think it can be anything but freeware. Remember that with freeware it doesn't necessarily mean that you absolutely have no choice but to make it available just because you have it, but you can't prevent other ppl from using it and distributin it once they have it, despite it being yours, because it is creating a file that is copyrighted by Epic, and if ppl had to pay for the program, the program's creator would benefit from something that Epic created, without paying Epic back. Now, the only way you could turn it into something commercial would be to have Epic's permission to sell it.