Unfortunately, I couldn't resolve the issue, as the only option is to buy a certificate for 60 usd/month, which isn't worth it for me. You can still compile the game yourself, from the source files located on GitHub.
I'm really sorry to hear that you couldn't resolve the issue. :(
It's clear looking at the source that a lot of work went into the project. Thanks for going through the effort to make and share this project. I hope the example you provided in github helps others.
