Short version: feel free & safe to use the Forum again. The old posts might or might not be added to the posts we post from now on later.
Longer version: there is still hope that the files (and posts) will be restored but of course no guarantee. Having a job doesn't help the server administration spend money on trying to restore the files.
However, I was assured, that the posts we write from now on will be preserved, even if the old posts get restored. I told otherwise in a previous post's comment before.
I'm sure you are curious about whether the forum software is responsible for the data loss. It is not. It was me, not bothering to check whether the posts get saved in the database or not. The default behavior is to save to files, saving to db would have to be enabled.