Some sad news, the original community member who bootstrapped the PowerPC port for the unofficial 14.04 release had left the forums and took down the links. 
If anyone has the image ubuntu-mate-14.04.1-dev.34508-desktop-powerpc.iso, then they could create a torrent, the hashes remain to know if it's the exact file:
md5sum 2bb57b2bbf87b668a94c38dd0393b263
sha1sum 9fe995a2832e2c0bcce5604b08095fb7217882ac
sha256sum b53d2836c00a2f9180353e908f09ee9eb4b17138dcc72bf692c6bd68b2756032
@Wimpy may still have a copy, we'll have to see.
I'd personally stick with the official releases (15.04 onwards) and investigate the error. There's always 16.04 LTS due in 2 months.
Edit: We have the file! See this topic: Download old releases of Ubuntu MATE