Hey, http://code.google.com/p/memcached/wiki/NewDevelopmentProcess ^ I've updated this page to hopefully reflect reality now.
Since it's taking so long to stabilize the 1.6 tree, I've decided to revive the 1.4 tree. We will begin again to make regular releases of 1.4 and 1.6 will track on its own until such time as it is no longer necessary to work on 1.4. So if you have bug reports, small feature requests, etc, we will take them for 1.4. I will do my best to cut a new -rc of 1.4 at a maximum of 3 weeks apart from the previous release, but if interesting things sit in the tree we should be trying to release even sooner than that. The 1.6 tree will continue to see beta releases whenever something interesting happens. The engine-pu branch receives random upstream merges, but I am not able to personally follow them very closely. -Dormando