After trying maybe 5 different versions of Ubuntu, Gentoo, Debian and MintPPC 11, I finally found a combination which works, and I thought I'd share it for the HUGE masses of people wanting to run XBMC on a cpu which has no support whatsoever from anyone :-)
Note: The problems I had were related to the Radeon graphics cards. I don't have any ppc machines with nvidia cards, so no idea if the problems apply for nvidia cards.
The problem is that in somewhat recent versions of the linux kernel, UMS (User Mode Setting), a method of 3D acceleration, has been removed and replaced with KMS (Kernel Mode Setting). But, on ppc at least, the Radeon cards don't play well with KMS. In fact, it's very, very unstable, and pretty unusable. Downgrading kernel and drivers could probably work, but I ended up in dependency hell when I fooled around with it, so I gave up pretty soon.
But finally I found MintPPC 9. Only a few tweaks were needed for XBMC to compile.
MintPPC 9 is really nice, since all the hardware works out of the box, flawlessly. Bluetooth, WiFi, sound etc, and with good 3D acceleration using UMS!
So, on to XBMC. Almost everything in the README file on github applies to the ppc platform, with a few exceptions.
$ sudo apt-get install git-core
$ cd $HOME
$ git clone git://github.com/xbmc/xbmc.git xbmc
Nothing strange there. One tweaks are needed for the dependencies though:
$ sudo apt-get install automake bison build-essential cmake curl cvs default-jre fp-compiler gawk gdc gettext git-core gperf libasound2-dev libass-dev libboost-dev libboost-thread-dev libbz2-dev libcap-dev libcdio-dev libcurl3 libcurl4-gnutls-dev libdbus-1-dev libenca-dev libflac-dev libfontconfig-dev libfreetype6-dev libfribidi-dev libglew-dev libhal-dev libhal-storage-dev libiso9660-dev libjasper-dev libjpeg-dev liblzo2-dev libmad0-dev libmicrohttpd-dev libmodplug-dev libmpeg2-4-dev libmpeg3-dev libmysqlclient-dev libogg-dev libogg-dev libpcre3-dev libplist-dev libpng-dev libpulse-dev libsamplerate-dev libsdl-dev libsdl-gfx1.2-dev libsdl-image1.2-dev libsdl-mixer1.2-dev libsmbclient-dev libsqlite3-dev libssh-dev libssl-dev libtiff-dev libtinyxml-dev libtool libudev-dev libusb-dev libvdpau-dev libvorbisenc2 libxmu-dev libxrandr-dev libxrender-dev libxt-dev libyajl-dev mesa-utils nasm pmount python-dev python-imaging python-sqlite swig unzip yasm zip zlib1g-dev
On MintPPC, libsqlite3-dev has a version mismatch with libsqlite3. Use the version located here instead.
We need a new version of taglib than what is available. We supply a Makefile in
lib/taglib to make it easy to install into /usr/local.
$ sudo apt-get remove libtag1-dev
$ make -C lib/taglib
$ sudo make -C lib/taglib install
Next, we run into a problem with one of the libraries being from the stone ages, namely libdbus-1-dev. But, googling around, I found a nice dev had made a patch for the file in question, LogindUPowerSyscall.cpp, being discussed here with the patch located here. Apply the patch and then it's all smooth sailing from there :-)
If you want Airplay, you also need to install avahi-daemon.
Speaking of Airplay, I've only gotten Airplay to work with the youtube app so far, not from Spotify. Looking around the forums, it appears that Spotify does some kind of "Fair Play" handshake with Airplay which isn't cracked yet, hence not in XBMC. But it works on my desktop machine, a Hackintosh. But could be that it's because it's running an Apple OS? Tbh, I have no idea about this, I don't have any other running XBMC boxes I can try with unfortunately. Anyone know for sure how this works?
This post is as much for myself when I need to re-install in a year or so, since I'll probably forget everything! But, there are a handful of people out there with ppc machines collecting dust, and they do make decent media boxes, for content up to 720. 1080 is a no-no, but still, if you have for instance an iMac G5 or an old Mac Mini that you don't know what to do with, they do make good looking media boxes!
Oh, and the PVR addons compile and install without problems, but I haven't been able to try it yet, as both my dvb-s cards got fried in a recent powersurge :-(
Biggest drawback of using a ppc machine as a mediabox now, is that there is no libspotify for linux-ppc, but at least XBMC is working, albeit without Airplay (Airtunes).
I hope this will save someone the insane headaches that Radeon drivers gives on linux-ppc, and answers the question whether or not it's possible to run XBMC on ppc after support officially got dropped.