The Catweasel is a somewhat flexible Floppy Disk Controller for both the Amiga and PC, though we generally refer to the PC version. It enables the PC to read a myriad of disk formats just like the Amiga, but with the added benefit of being able to add different sorts of disk drives out of the box. See the website for more information.
With regards to SPS supporting the Catweasel for dumping or re-writing:
Due to technical reasons, the availability of KryoFlux in early 2010 and because Catweasel seems to us fairly outdated today, we have chosen not to support Catweasel with any further development.