PIXEL is only built for either the Raspberry Pi (ARM) or standard PC (x86) architectures. It will not run on a Power Mac (PowerPC).
I recommend Ubuntu MATE 16.04 LTS or Lubuntu 16.04 LTS. Burn either image to a CD and boot by holding C (IIRC) as the Mac powers on. Make sure you download the images labeled PowerPC.
This FTP server seems to work on PowerPC.
http://download.cnet.com/CrossFTP-Server/3000-2160_4-172615.html
You other option is to install a PowerPC version of a Linux Distro such as Ubuntu. This is a lot harder to do, and things may not run smoothly depending on your specs.
Debian dropped support for PPC in Jessie, and it looks like you were asking about earlier versions which definitely had PPC support. When I go to the official Debian Ports page for it there seems to be a load of information.
The most reliable Debian-based solution though may be Mint PPC . According to this article (and their actual website) has a version of Mint PPC, based on Debian Sid, available in 32-bit and 64-bit versions.
USBs made with unetbootin will not be usable on powerpc macs
that's why. I recommend using dd. It might be a little more complicated, but you can be sure that it will work.
I finally cracked it. I followed your instuctions for yaboot howerver acceleartion was still unavailable. The only lead I got left was glxinfo failing to start - happened to me before - but following your instructions on clean system I wanted to make sure, that I did everything else correctly (since you got it working).
I went trough xorg error log and I found an entry saying "At least 43200 kB of video memory needed at this resolution and depth." So I lowered the default color depth in xorg.conf and acceleration started to work.
Note: I don't really understand, why xorg thought I need 43MB of video memory. Did some calculations according to http://superuser.com/questions/256932/how-do-i-calculate-video-ram-requirements and one frame requires around 6.6MB - I was using 1920x1200x24 - (not sure about the framebuffer though)
Regarding missread version of package: Interesting accident cause Ubuntu recommends using 7.11 https://wiki.ubuntu.com/PowerPCKnownIssues#A12.04_Precise_Pangolin
Edit: Forgot to say: Thanks for all the help! Especially in showing that it is possible to get acceleration working.
Uh.. Owncloud is free. I didn't/don't pay a penny. https://owncloud.org/download/ Works great. Even has shared webmail and Calendar functions if you want to set it up.