Nokia is moving to a single sign-on experience using Nokia Account – this account will allow you to access all Nokia Services, including Nokia Store, Nokia Maps, Nokia Music, and now Nokia Publish and Nokia Developer.
The deployment should occur this morning (Wednesday 27/6/2012) Finland time.
There is more information in the FAQ.
P.S. If you’re using Nokia Projects, you’ll also need to authenticate against your Nokia Account username in order to use the version control system.