I’ve released DoFollow 2.0 to go with WordPress 1.5.1. The functionality is the same as before, and the plugin can be used with (an unpatched) 1.5 as well.
The patch I had proposed to core WordPress functionality is gone: the developers prefer to keep the current nofollow implementation as is. If you had previously applied the patch, you can download a copy from Mosquito issue #1087 and reverse it (e.g. using patch -p -R).
I wanted to make this change to DoFollow, as it removes a chunk of code that was digging in some internal structures of WordPress that don’t have an exposed and documented API. Now it is much less likely that changes to DoFollow would be required for maintaining compatibility with future WordPress releases.