Forked from the then-stagnating (and now seemingly dead) Waimea window manager, Kahakai sprang to life in late May of 2003. A fair number of members of the #waimea IRC channel on Freenode were tired of waiting around, and decided that it was feasible to take Waimea to bigger and better places. The main feature in mind was integrated scriptability -- not in one language, but many. This was seen as the natural evolution of Waimea's already powerful actions system. SWIG was chosen for its wide range of supported languages, and work began initally on Python. As of this writing, Ruby support is mostly complete, with some small kinks left to work out and refine.
Naturally, many other things began to change, be removed, added, and reworked. Kahakai is now very much a huge leap beyond what Waimea was, both in scripting abilities, and in all other aspects. Development continues, and at roughly 4.5 months old (at time of writing, of course :), Kahakai still has a lot of room to grow.