That shows "contributors". It looks like they have roughly 4 regular contributors. Their Github org lists 5 members. I would not consider that "a lot".
Seems like everyone that has contributed should get a percentage of all commercial licenses sold.
To some extent that's reasonable, but I would set a cutoff. If the cutoff is 0.5% of changes that would be about 10 people. If it's 3% then that's only 4 people. If it's 0.1% that's about 20 people, and that already seems like overkill.