The AquaTerm detection that has been added to 5.0 fails to work on case sensitive file systems. The framework is installed as "AquaTerm" (with uppercase "Term").
I'm attaching a patch to fix that problem (it fixes a few more places than just the bare minimum, but in my opinion it's nicer to be consistent).
See also https://trac.macports.org/ticket/46942 for the original bug report.
Thanks a lot for the fix.