plasMatrix Free is Freeware and has a limited functional scope. Limitations are:

Works with JPEG files only.
Accepts only one file per Drag&Drop.
Cannot save Settings.

plasMatrix Pro is a commercial version and has to be purchased. In return it offers an extended functional scope, like:

Works with JPEG, Bitmap, GIF and PNG files.
Accepts virtually unlimited files pre Drag&Drop.
Can save Filter Settings to re-use them as Preset.