Is the task journal data stored in a sqlite database? Is this something that can be connected to in order to mine/report data from the task journal via methods other than the server interface?
The embedded (default) database for the journal is SQLite. See here: Where is the embedded journal DB?
You can connect to it and query with anything that can query a database. If I remember it correctly, someone posted on the Community forum a nice dashboard built on top of the journal DB.
In the Enterprise edition, it’s possible to use an external database (SQL Server or Postgres) as the journal database. It also can be queried.