I used Pygmy Linux which was similar -- it installed in a subdirectory of an existing DOS install and booted with LOADLIN. It was quite useful -- for example it was a simple effective way to probe IDE disk types and parameters, far easier than using multiple DOS utilities and cross-referencing.

DR-DOS is still around and I have been working on getting some updates working. https://liam-on-linux.livejournal.com/58013.html