The respository has two channels, 5-0 and 5-1, which is really HEAD. Which channel your server uses is automatic, based on your kernel version. A server using the 5.0.0 tarball uses channel 5-0. Due to a bug in the code generating the repository, the 5-0 channel actually had HEAD code. Lars fixed the bug and I rebuilt the repository on openacs.org a few hours ago so "Install from Repository" should produce much better results now.