Thanks to Yann Hodique‘s totally awesome
backend structure in hodique@lifl.fr—test/planner—merge—1.0, the distinction between planner/emacs-wiki and planner/muse is on the way to disappearing. Yann's Elisp-fu is far beyond mine, and it shows in the elegance and cleanliness of the backend code.

It's much, much better than my kludgy attempts when I wrote the first
port of Planner to Muse. I kept running into problems thinking of an
elegant way to combine both backends. I just wanted to get Planner out
the door, so I tagged a new branch and replaced all the emacs-wiki
code with muse equivalents.

That spurred a lot of development on the planner-muse front, and we
blessed Michael Olson's tree as the canonical planner-muse branch.
Keeping up with patches became a real headache, though, because of all
the translation between branches.

I've tagged a new tree off Yann Hodique's branch and made emacs-wiki
work again. I've also brought it up to the latest dev (I think!), and
I'll be using it for the next few weeks. A number of modules still
require emacs-wiki, and with the Planner community's help, we hope to
open them up to Muse people as well!

You can grab the merged tree with

tla register-archive http://sacha.free.net.ph/notebook/arch
tla get sacha@free.net.ph--main/planner--merge--1.0 planner

Back up your plans and customize planner-backend. Have fun!