For anyone who wants to follow the effort to revive MUSS, I have started a project on GitHub. You can find the repository here. The initial effort is focussed on creating FLIP to translate the Flocoder to compilable MUSL and I have made a start on that.
Once I have FLIP then I will need to start the process of compiling MUSL. I will probably compile the MUSL to C and then compile the original MUSL compiler (written in MUSL), but that is a little bit further off.
Rob's Old Computers 
It’s fitting that Flex and Bison (language scanner and parser – parts of a compiler-compiler) are used to process Flocoder files as the late great Derek Morris was one of the main contributors (together with Tony Brooker as the lead) to the Atlas compiler-compiler, which was the first of its kind and which spawned yacc. Derek was also one of the prime movers behind Flocoder and its enforced use for MUSS and other software.
Although never achieved (as far as I know), at one stage there were plans for CS104 and CS204 course students (1st year and 2nd year systems software courses) to use Flocoder for their PDP-11 assembler assignments – and Flocoder was ideal for use with assembler. At that time, all assignments were in two parts – with the first part being the program design including a hand-drawn flowchart. It was envisaged that the 16 tele-types connected to the PDP-11/20 (front-ended to the PDP-11/40 that executed the programs) would be able to have access to the MU5 computer so that Flocoder could process their locally-held files and produce the flowcharts on the PDP-11/40 (which used an early version of MUSS from 1974) plotter. However, the connection between the two systems never worked satisfactorily (despite being a third-year project for two years) and so was abandoned as far as I know.