Here's a video of me testing it out in October 2018:
I had one easy to fix bug when media was on APFS formatted hard drives,
and have not yet met or heard from anyone else that's had the same bug,
so it may have just been because I was booting Mojave from an external USB drive.
There is a poll on the Media 100 Facebook Group, about which MacOS version Media 100 users are using.
Thirteen people have responded to the poll so far,
and one person was using MacOS 10.14, three people were using MacOS 10.14.1 and one person was using MacOS 10.14.3 - so that's five people happily running Media 100 on MacOS Mojave.