And here is a disassembly for the versions 1,2,3 apparently: https://www.memotech.franken.de/CPM80/
Added: the comments in those files are better than nothing but they don't really say what the program is doing the way the original source code hopefully would. The labels are still the ones generated by the disassembler, so not very informative. Still, it's nice that someone did this and it's a good starting point for further study by anyone sufficiently motivated.
If of any interest, the source code to the BDS C compiler of the same era was released here: https://www.bdsoft.com/resources/bdsc.html
It discusses TP 3.0's operation, supposedly based on a disassembly. It's less interesting than it sounds (it's mostly a high level overview of how a small compiler works, rather than a real study of TP internals), but it helps.
Long TP discussion thread with dead link here: https://news.ycombinator.com/item?id=10202299