While not the very latest, I was able to (this is on amd64, although it shouldn't matter) simply cp htmltidy-3.10.29.ebuild htmltidy-4.07.04.ebuild and it worked just fine. The latest tarballed (rather than cvs) release upstream is at the moment, I think, 040706, but 040704 is the latest that's in the old/ directory, which means no necessary change to the inside of the ebuild.
Added 040806 to CVS. Thanks for the report.
same thing for 040806