jwm was removed from the tc-5.x repo because it had been compiled with a dep on libpng12 - I just checked jwm-snapshot and it has also been compiled with a dep on libpng12. In addition to this, jwm-snapshot lists Xorg-7.6-lib as a dep, which is also not present in the tc-5.x repo.
To be in the tc-5.x repo, both jwm and jwm-snapshot need to be compiled with a dep on the version of libpng in tc-5.x, which is libpng16.
I don't use the coreplus iso, but I would assume it included jwm believing the version in the tc-5.x repo worked on tc-5.x, which proved not to be the case.
Both jwm and jwm-snapshot have been removed from the tc-5.x repo until they are recompiled for tc-5.x