Is there an official location for this project, with source code etc.? Forgive me if I sound paranoid, but downloading a binary from a random Dropbox is a little weird.

Looking in the README, it appears that this OS X branch is part of the main repository. The page for it is at https://code.launchpad.net/~suv-lp/inkscape/osxmenu

It is VERY weird. However, that dropbox link is indeed on the launchpad page that robotfelix posted. If you trust the page, I suppose you can trust the dropbox link.

I wonder if there's any chance it could be made to work on Homebrew...?