Since we are experiencing a huge wave of spam during these days, I have temporarily switched user accounts creation from "free" to "need administrator approval".

In the meanwhile we will work on finding a solution to prevent spammer accounts creation.

Sorry for the inconvenience.

Ok, we have activated reCaptcha support for user creation, the need of administration approval has been removed. We have also pruned the database from spammer accounts.

Hope it is all ok now!