I just found out about this today. I am not in the Discord, so I don't know what was discussed there.
From my searches, people are falling into two camps, to avoid this happening again. They are saying code your own engine from scratch, or use open source. But if OurMachinery's engine was based around an idea that is patented, then neither of these approaches would stop this situation happening again.
I saw a tweet by Casey some time ago, where he said a certain company has ECS patented. So perhaps this company enforced its patent? If so, then even if you make your own engine from scratch, or use open source, the same could happen to you if you use ECS. So the lesson could be, make sure that the software you are using or building is not patented.
BTW I am not pro patent. Out of all the theories I have seen, I think that is the most likely.