Every time someone use his package management system to update an installation via builbot the message:
WARNING: The following packages cannot be authenticated!
Install these packages without verification [y/N]? y
Get:1 http://buildbot.linuxcnc.org/ precise/master-sim linuxcnc-doc-de all 1:2.6.0~pre0.3273.gc11d5a8 [8650 kB]
So please provide a proper key for the buildbot packages.