For anyone that still wants to use this for the 0.6.0 release, I've made some patches with slight modifications to David's code. It's split up into two parts. The first part should still be relevant for pool operators (keep-alive connections, hub mode, USR1 signals on block changes). The second part is mostly obsolete now with merged mining and better pooling software (faster getwork).
You can find the patches at http://pastebin.com/viJV1NLi
Some of the updates from 0.4 to 0.6 are non-trivial so this should help. This particular patch hasn't been tested much but a different one for 0.6.0 rc4 has been running without any problems.
Edit: Oops, the patches were for the current head instead of 0.6.0.
Edit2: Updated the above links for the right patches.
For future reference, these may give you a head start on patching against 0.6.1: http://pastebin.com/XSBqRAaP