On the project page (http://musicpd.org/gmpc.shtml), the latest release still
seems to be 0.11.2. The 0.12 tarball is also unavailable on the download site.

I have asked the gmpc author, and he sent me this link to the release
with an explanation:
----
here is a little story about it:
http://etomite.qballcow.nl/qgmpc-0.12.html

the problem is that I am low on time, and don't really like doing
website stuff.

I'm sorry,
----

There is already a gmpc-0.13.0 (which requires a new library, libmpd-0.12.0, to
compile). I have created new RPMs of libmpd, and also RPMs of gmpc, based on the
one from FC5 extras. All the files are available at
ftp://ftp.linux.cz/pub/linux/people/jan_kasprzak/gmpc/.

Aurelien, feel free to take these files and include it into Fedora Extras,
or tell me that I should submit libmpd myself (or even take over the gmpc
package maitanership).

> or tell me that I should submit libmpd myself (or even take over the gmpc
> package maitanership).

Actually, that would be the best solution, since I don't use mpd/gmpc myself
anymore.
Submit libmpd and I'll review it, you can take over gmpc afterwards if you want.
There is also mpc, the command-line client, that you may want to take over (it's
very little maintenance). It's up to you.

gmpc has been updated 0.13.0 for FC-5, FC-6 and for the devel branch