Dimitry Yemanov announced :

The project repository was migrated to GitHub:
https://github.com/FirebirdSQL/firebird

Please wait a few days for things to settle down, we need to update some
infrastructure. SVN repository is still accessible, but new
contributions are expected to be provided as pull requests at GitHub.

When creating a GitHub account, we suggest to add your SourceForge’s
email (username@users.sourceforge.net) as a secondary one to associate
your past contributions with your account.