I just got this sourceport but there is no sound at all, neither music nor sound effects.

The only sound option it gives is "Open AL Soft" which I assume I have because it would not be shown in the menu otherwise. However, running the game outputs no sound at all, not even when I change the MIDI synth option.

What the hell do I do to fix it?

Sometimes I find that the sound turns off on my copy, or it did. I would have to restart it and check the in-game audio options menu, there's an option called sound, if it's off, turn it back on. If that is the issue, it might turn itself back off on a later startup, but you can repeat the process.

I think I saw someone else who had an issue with sounds related to them using JRE9 instead of 8 or something like that, too.

It shows the sound is on so that's not the issue. I did find an alternate version that does have sound, but now the FMVs refuse to play. I followed the game's advice and extracted the movie folder from the gog file to the main folder too and it still didn't work.

I also just tested and found out that I can just enable them in a menu (which I didn't notice, the new version doesn't have it so I switched back to the old jar file while keeping the rest) but that breaks the sound and prevents it working again.

How do I get the FMVs working properly now as well as the sound?

I am using version 789.

Hm. I actually haven't gotten around to putting the FMVs in myself, though the ones from user levels work. Have you checked your Java version? As I mentioned, I did see that someone had an issue that was resolved through using JRE8 instead of 9 (I actually use a portable Java solution, myself, so I'm not quite in the same environment).

It's OK. I've now found a way around it though I can't remember how I did it.

Huh, well, at least it's working, have fun!

I'm using JRE v9.04 (64-bit) myself and haven't had any issues.