clens is a convenience library that aids in porting code from OpenBSD to different operating systems. Operating systems traditionally have different enough APIs that porting code is painful and can litter pretty code with ugly #ifdefs. In order to keep code readable and drastically reduce the number of #ifdefs needed, clens brings other APIs or missing functions into specific OS "focus".
m9u is a music server, similar to mpd or xmms2. It sits in the background, waiting for commands to be delivered via a 9p file system. m9u embraces the Unix philosophy of doing one thing well. As such, it does not try to catalog or otherwise organize music, but aims for the more humble goal of simply playing it. A side effect of this approach is that m9u is trivially extensible to domains aside from music (for example, an image slideshow).