Seeing as that Greece is a member of the EU, I don’t think they will be successful in implementing a ban, any more so than Italy or Sweden or the Netherlands will be in the long run.
Yes, they can be a pain in the ass for the time being – but ultimately unless EU regulations are changed, they will have to allow equal access to their markets from other EU members – and you can be sure that gambling services will be allowed in the end.
If you’re not based in an EU country – well, it’s not that hard to register a company in one of those jurisdictions, surely…