Hi Urs,
I had such poor results with abc2ly just recently that I can't imagine there is any user base using it in earnest, or even at all, else there would be lots of complaints. Or perhaps I was doing something wrong. I feel that it does not deserve a place in the stable.
I think instead of including another open source distribution inside our program distribution, we just have an NR section that mentions how to import ABC, using the existing musicxml2ly program. I think anybody wanting to do this sort of thing can cobble together their own shell pipelines, and download abc2xml themselves, given the pointer to it (which is all that I was missing).
Andrew
It sounds reasonable to drop the current abc2ly implementation.
However, I think we shouldn't do this without somehow including
abc2xml in the distribution and (probably) create a wrapper script
abc2ly that transparently replaces the old implementation and
calls abc2xml | musicxml2ly instead.