Mapache's error log is saying:
"[Mon Nov 11 13:46:02 2013] [error] [client 127.0.0.1] client denied by server configuration: F:/Vegas/HowTo/DokuWikiStick/dokuwiki/data/security.png, referer:
http://localhost:8800/doku.php?id=start&do=admin"
I enabled the "allowdebug" option, however \dokuwiki\data\cache\debug.log is only saying messages.txt is up to date. messages.txt doesn't contain any information. What else do I have to do to enable debug logging?
Is the second and third link working in your browser? My browser is not showing or offering a download, only the first link works. Perhaps it is an issue of the network (university). I am going to try it at home tonight.
Edit:
Ok, it seems to be a problem of the network or a combination of my network and github. I could successfully install mediasyntax plugin from this url:
http://www.staerk.de/files/mediasyntax.tar.gz