As usual, the law. Registering in a database it's not equivalent to stopping from doing business.
Discussion
How does open source fit into that? Do open source devs need to register too? If so, it seems like a burden on open source and not so much of anything to big players who probably have teams to deal with this type of thing.
We don't know yet. But from that article I don't see any problems. Just goes along with the usual EU personal data protection laws.