The author of this patch is 'toby' from the MacPorts project, and the original commit containing this diff can be found at https://trac.macports.org/changeset/58563. The trac ticket prompting the commit (and with additional context) is at https://trac.macports.org/ticket/18357.
Toby, if you're reading this, apologies for not attributing the gist originally; I put this up quickly while experimenting with tmux under Leopard and abandoned it when it didn't solve the problem at hand. It's only fair now that other people are looking at the gist to give you credit.
I tried applying this patch to tmux 1.4, but no success. It compiles, but pbcopy still does not work. Any success messages out there?