I won't insist on adding it. If
xemacs.org doesn't want to distribute
non-GPL elisp code I think a "non-free" XEmacs package repository
could be useful, similar to non-free Debian packages.
Such a repository may encourage people to re-implement the software
under GPL, which would be what I'd like to see eventually.
Actually distributing the software encourages people to use it, not
reimplement it.
The way to encourage reimplementation is with a task list which gives
descriptions of the jobs to be done, and mentions the names of
programs to be replaced for the sake of people who already know them.
If a person says he is seriously interested in doing a certain job,
you would tell him where to find the program to be replaced, in case
that's useful for him.