Five years ago, the NetBSD project celebrated the 10-year anniversary of their package management facility, pkgsrc, by interviewing many *BSD luminaries about their ports and packages systems. Though the interviews were pkgsrc focused, you can glean much about the approaches each project has taken. OpenBSD's approach is very well described by Marc Espie, the lead developer of the OpenBSD Project's pkg tools.
http://www.netbsd.org/gallery/10years.html