>> Resolving bug report 892 includes important patches to reduce potential
>> conflict with KDE4 and to make our own *.desktop files XDG compliant
>> (recently Trinity/TDE was added to the list of registered environments:
>> http://standards.freedesktop.org/menu-spec/latest/apb.html).
>>
>> Resolving this bug report is important to release R14.
> <snip>
>
> I am fairly certain that what you are looking for is in the file
> cmake/modules/TDESetupPaths.cmake, specifically the line which sets
> XDG_APPS_INSTALL_DIR
>
> tde-config is generate from tdecore/tde-config.cpp.cmake, which uses
> XDG_APPS_INSTALL_DIR as defined during the build process.
>
> Tim

There is a second hardcode for the Autotools build system in
admin/acinclude.m4.in, line 535.  It looks like this:
xdg_appsdir='\${datadir}/applications/kde'

Tim