I have written a library called lib3to6.

I am unsure of the most appropriate way to add lib3to6 to python3statement.org, since a large part of the purpose (though not the whole purpose) of lib3to6 is to help with backwards compatibility for Python 2.7. In that sense, the project would not be appropriate to add to the list of participating projects.

I do feel however (biased as I am) that for some libraries, lib3to6 makes it very cheap to support Python 2.7. The most recent example where I did this was with the pretty-traceback package.

I assume there are at least some packages that currently support both Python2 and Python3, which could benefit from this kind of automated compilation/transpilation, but who are not aware of lib3to6 as an option. They could start to use many of the Python3 language features and associated tooling such as mypy, remove much of the boilerplate such as from __future__ import print_function from their source repository and nonetheless retain support for Python2.7 if that is important to their users. In this way, lib3to6 can reduce the burden on maintainers to continue supporting Python2.7 if they still need to.

If/how to add lib3to6 to python3statement.org, I'm not sure. Perhaps a mention on the practicalities page would be appropriate.