see the sticky in this forum
https://us.forums.blizzard.com/en/wow/t/ui-add-on-development-policy/24534
theyve gotten pretty explicit about it lately. ie you used to be able to charge for support, or charge for access to a web site where they offered more offline stuff, that sort of thing, but that text above is pretty explicit - no money for anything related to the addon.
it will probably depend on how much they annoy players and those players then report them to blizzard.
you wont get banned for using it no matter what as is not exploiting anything.
best case blizzard tell them to stop charging. worse case blizzard will just block their addon so it wont work in game.
there are other completely free alternatives out there for levelling