You mentioned it was using Bluetooth to communicate with the actual machine so I’m assuming they are not directly connected to the internet in any way? If that’s correct then it’s just a case of understanding the Bluetooth comms which is probably some basic BLE stuff they put together by tweaking the sample code from the BLE chip manufacturer.

I’d be ripping that app apart and patching it to skip the payment step.

Honestly it just works and works well. I had all sorts of issues with Plex with subtitles not working and weird transcoding issues where red blocks would randomly appear. Also I found Plex kinda ugly tbh. I tried Jellyfin and it seemed a bit ‘hacky’ but this was a few years ago so maybe it’s improved but I currently have no reason to try it again. If you’re using Plex/Jellyfin/Emby you are most likely pirating media so worrying about GPL violations is probably not top of the list.

Try Emby. It’s a more polished Jellyfin although it’s not FOSS I find it much better than Plex

As a former director of a tech startup it all goes downhill when you bring investors on board to raise capital. I had to do many things I disagreed with because once you bring investors in you generally end up facing life ruining financial penalties if you don’t deliver what they want.

Yep I know. I just found it to be poorer quality. Emby is much more polished.

People should try emby instead. I find it the best of the 3 main contenders.