Thanks guys!
I've got PPaint version 6.4, that's the last free version if I'm not mistaking. But the script makes it attractive to buy the latest version. I'll look into it.
In the mean time I've found a nice little tool at Aminet called
Anim2GIF. I haven't tried it yet, but it might do the job.
Emufan, I didn't know there's an ffmpeg version for MacOS. Thanks, I'll check that out too.
As far as I know there's no animpaint function in PPaint 6.4. I'd love to use DPaint's animpainting, but I'm currently stuck due to an issue that causes the Alt key to not work simulatenously with the left mouse button in FS-UAE for MacOS. I've entered the issue in the FS-UAE bug tracker, and hope it will be fixed soon.