The development snapshots are unofficial packages extracted from the SVN on a non-regular basis. Each snapshot reflects the SVN state on a particular date and you're likely to find a really recent one. The packages have been tested on at least a couple of systems and have a good possibility to compile on yours. There are also some binary builds available.
The source snapshots are kindly provided by the KVIrc Development Team.
Honor and Glory! :)
To download the latest snapshot you have to dig in the KVIrc ftp or in the "snapshots" subdirectory of one of the ftp mirrors.