It doesn't look like there's an official one. The README file for the new version (wow — about time!) says
Building on other platforms
(On the darkside OS, who hijacked a common word for fenestration)
I use MinGW and MSYS. (Use mingw-get to download gnu build tools perl,
automake etc.) However it doesn't install plugins properly. You will
need to copy files to the proper Gimp plugin install directory,
typically from:
c:\MSYS\1.0\usr\local\lib\gimp\2.0\plug-ins to:
c:\Doc...Settings\yourname.gimp-2.6\plug-ins
.. which suggests that there's no official binaries or installer, and that the programmer isn't particularly interested in that. MinGW is a relatively — when compared to very complicated alternatives — system for building unix-like programs on Windows, or building them on Linux to run on Windows. And MSYS is a shell system for basically making the Windows command line more like Linux. Honestly, I'm not sure why one would do that instead of just running Linux.
In the comments to the registry.gimp.org page you link to, though, there's this one, where someone named "samj" has built binaries. If you trust running random programs from comments, you can download the binaries from there. It seems reasonably trustworthy to me, really — the install instructions in the included lisez-moi.txt file look legit (and are basically understandable even if, like me, you don't speak French) — basically, copy all the files to C:\Users\[username]\.gimp-2.6\plug-ins and it should work. (You'll probably also need Python for Windows installed — that's a whole 'nuther thing.)
Or, you know, you could switch to Linux where this is all just trivially easy. :)
