even though Sparrow hasn't been updated for quite a while, the forum still contains a lot of information that shouldn't be lost. However, the old forum engine really showed its age – and, more importantly, was running on a PHP version that's no longer receiving security updates. So I took the effort and migrated all data to a shiny new forum engine (Flarum).
However, this also means that all your passwords have been reset. To log in, you first need to request a new password, which can be done by clicking on the "Lost Password?" link in the login panel.