When I lookup the "files" for the latest version (0.8b3), I see "linux-i686", "macosx", "windows" and "win32-no-msvc70". Maybe the Mac versions are 32/64 bit "Universal builds", it's hard to tell; "windows" is subdivided into "zip" and "exe", it looks like it's 32-bit only but no certainty; one thing is sure: the Linux builds are 32-bit builds (in various languages).

64-bit computers and the OSes to go with then are becoming more and more of a household commodity, almost dirt cheap even — if you don't insist on the very latest bells and whistles. How about distributing 64-bit prebuilt versions of Kompozer?