Hi, I have made this boot-loader 
I finally got to integrate the free FFT stuff into my git tree (which had the open-source 3.11 + my “infrastructure” fixes to build with gcc and IAR4/5 from common code but not much new features). For now it is in a separate fft-relocated branch at gitorious.org/dsonano/dso-firmware . I also intend to merge the later released open-source 3.13 code, which will simplify code relocation (more on that later). I have not pushed it to my master branch yet, awaiting some rebasing to make the merges cleaner.
I think I will post more on the boot-loader work in a new thread, but using it for dual-booting Benf and the free FFT version seemed like a good demonstration of it. The boot loader is work in progress and the implementation here to select BenF/FFT is just a hack. Instructions are in the zip-file.
I hope this can encourage more development on the DSO Nano!
Note: This only works with the old USB bootloader, not the new “HEX” file-based bootloader firmware.
DSO-Benf-FFT-dualboot.zip (33 KB)