[Tim Wood]

This a backup file to replace your current database perfectly OK (make sure you copy instead of moving it). In fact, this is exactly what OmniFocus does when you select File > Revert to Database Backup…

You can merge all the transactions into one via the File > Rebuild Database… menu. In the future, we hope to make transaction coalescing more automatic, but this didn't make it into 1.0 early enough (this would be a potentially destabilizing change and there is a workaround, if a little manual & hokey).