Starting with version 0.21.0 of POPFile, the backend database is an SQL database. POPFile ships configured to use SQLite, but can be reconfigured to use any SQL database that is supported by Perl's DBI.
These instructions are specific to PostgreSQL, but could easily be adapted to any supported SQL Server.
Should you find anything in the documentation that is incomplete, unclear, outdated or just plain wrong, please let us know and leave a note in the Documentation Forum.