Questions about server usage of axiom (non-commercial)

[queen locust]

Does every player need the whitelist in order to join the server, or just the one running it?

Is axiom compatible with the regular 0-8 player servers run from the 'Essential Mod'?

Would a world made using axiom be negatively affected from it being removed at a later date (and would this world, if run as a server, require a license)?

[mossy owl]

Every player needs a whitelist
As far as I'm aware it works with Essential
No Axiom doesn't change anything with how the world is saved