Basically, yes, the campaign accepts users starting from Member rank. But at the moment, only Hero and Legendary ranks positions are open. You can keep an eye on this thread and see the changes on each Sunday evening or Monday, at last (forum time). This is the time when the manager (CryptopreneurBrainboss) announces the open positions.

With other words, you are eligble (your rank is eligible) but not at the moment. I hope this helps.