I desired to front tomcat with apache on AIX, but there's nothing in http://www.apache.org/dist/tomcat/tomcat-connectors/jk/binaries/aix and searching around was not successful. I eventually built it from source (painful as there's paperwork around obtaining the compilers installed only at that large corporate).

But should not this binary download exist somewhere? So why do they simply come with an empty directory?

My prediction is they do not have an AIX or FreeBSD (also not there) machine around to get it done. Possibly you can volunteer your build?

AIX isn't the only neglected platform.

General interrest and support for that mod_jk project appears to possess reduced since the development of mod_proxy_ajp in to the primary supply of apache-2.2

This modules performes essentially exactly the same functionality as mod_jk and doesn't need an additional install.

The version of apache-2.2 I acquired from http://gnome.bullfreeware.com/aixtoolbox/RPMS/ppc/apache/ also consists of this module.

It is possible to reason to obtain the binary and never compile it? You will get all of the source from apache's svn.