<mdl.int> contains Muddle for TOPS-20, from around 1981.
There should also be support for ITS, but it won't build as is.
<mdl.comp> contains a TOPS-20 Muddle compiler from around 1982.
<mdl.documentation> documents the 1979 ITS Muddle 54.
<sys.unsupported> contains a few progams in the Muddle ecosystem.
MUDDLE contains Muddle for ITS, from around 1973.
mim contains Machine-Independent MDL for TOPS-20 and VAX.