I submitted gource to slackbuilds.org and I’ve tried it with their repository

you can alternatively watch it with mplayer

mplayer http://ponce.cc/videos/other/slackbuilds-gource.mp4

first I got the avatars off gravatar with a perl script.

then the command I’ve used to do this (inside of the slackbuilds repository folder) is

gource -1280x800 -s 0.7 --user-image-dir .git/avatar/ --default-user-image \
  ../no_photo.png -a 0.25 --colour-images --bloom-multiplier 0.80 \
  --bloom-intensity 0.55 --user-scale 1.8 --user-friction 0.7 \
  --title "Slackbuild.org git history" --output-framerate 25 --disable-progress \
  --stop-at-end --output-ppm-stream - | ffmpeg -vpre libx264-default -y -b 3000K \
  -r 25 -f image2pipe -vcodec ppm -i - -vcodec libx264 ../gource.mp4