Is it possible to use this unit as a general purpose MIDI controller and to operate MIDI-compatible DJ software other than rekordbox dj?

When using the unit in combination with MIDI-compatible DJ software other than rekordbox dj, you need to configure the mapping settings yourself. For details on the MIDI assignment for each button and pad of the unit, check the AlphaTheta support page.

[Support] > [FIND SOFTWARE INFORMATION] > [DJ CONTROLLER] > [DDJ-XP1] > [MIDI-COMPATIBLE SOFTWARE] > [LIST OF MIDI MESSAGES]

Also, for information on the assignment procedure, refer to your DJ software's operating instructions.