You're trying to get them to talk to each other?
Discussion
Yes. I wanna use btcpay as a whitelist system for minecraft server. (User plays $1 in btc and on the form page they put their username, api call to white list that username)
The Minecraft API is JavaScript so I don't imagine it being too trivial. Just checking cursedforge and there are several whitelist plugins so it's definitely writeable. Should be able to trigger it on a successful payment.