Do I have to buy a Serato DJ Pro license and activate it?

It is not necessary.

Connecting the DDJ-1000SRT activates the Serato DJ Pro so that you can use the software when the unit is connected.

To use the Serato DJ Pro even when the DDJ-1000SRT is not connected, you may need a separate license.

For details, visit the Serato website [here] (https://serato.com/dj/pro/buy-dj-pro%22https://serato.com/dj/pro/buy-dj-pro%22)