There was 2 versions of Jasper Reports Server

• Community version (open sourced) - which is no longer available (8.2 was last one)
• Commercial version ("Professional" or "Enterprise") which add additional features to Community version, features are like Ad-Hoc, Domains, Multitenant repository, etc..

Usually you can check which version do you use by visiting "About" link in left bottom corner of UI.

About users:

• Community version have a user "jasperadmin" as a top level account.
• Commercial version have a user "superuser" as a top level account, "jasperadmin" is also present but it's highest account for an "Organization" not for a server

About adding JDBC driver, there are 2 different ways to adding JDBC driver:

• During Installation (in "JasperReports-Server-Install-Guide" there is a section how to do that)
• Add it in UI ( in "JasperReports-Server-Admin-Guide" there is a section "Managing JDBC Drivers" which describe how to do that)

I'm not sure if community version did have abilities to upload JDBC drivers in UI.