Kon,
DSS can do star trails just like the program Startrails.
Under "Stacking Parameters" and the "Light" tab, select "Maximum" for stacking mode. Normally this is set to average or median.
Secondly, go to the "Alignment" tab next to the "Light" tab and ensure you select "No Alignment" as you do not want DSS to align your images.
This will produce star trails.
Cheers,
Darrin...