de-GEL is a small utility written by Christopher D. Granz to extract RIGOL "GEL" firmware files.
This version has been modified to work with the DS-1000Z by ~ktemkin.
After taking a peek at the Rigol file format myself, I was lucky enough to stumble upon the de-GEL utility for the very-close GEL format used by other Rigol devices. A minor tweak, and it works for the DS-1000Z.