What about the BSL makes it a deal breaker? You can host it yourself you just can’t compete with their hosted offering to other customers. I think that’s fair: they get to monetize what they make. And then after 3 years iirc all the code that was BSL or that version anyway goes even more permissive.
I avoided language such as "deal breaker" or "problematic" and chose rather to just say "it would require discussion" in ways that I have not once ever encountered with an Apache licensed project.
Doesn’t seem to be one. They took the Kafka API so it’s a drop in replacement and redid the implementation from the ground up. Your mileage may vary though.
I am just worries that things like 3rd parties integrating with your Kafka broker will stop working or experience issues. Also, I wonder if SASL_SSL is implemented exactly the same way etc.
I don't have enough experience with these new vanity licenses to know what the contribution story looks like, either