You can send an email to support via their website to request a refund. That's going to be your only option, I'm afraid, as the stand-alone is not going to be updated to v1 and, as such, won't ever be able to produce a game without the warning screen.
Intel i9-10900K 5.10GHz, 64 GB RAM, Nvidia GTX 1080 ti 11GB, Windows 10 64-bit, dual monitor display