If qt3 is installed, there should be no need to build $(MOC). moc should be built by qt3-x11 (at least, qt3-mac does and puts it in /opt/local/bin/).
The MOC build target is not moc itself, which qt3 does install and in the right place, but the project's own source files that are preprocessed with moc. Moc is some sort of macro processor; that's all I know about it.
In principle, QT Apps should build provided you tell them QTDIR=/ opt/local (put ${prefix} instead of /opt/local) and if needed tweak the Makefile to tell where the bins and libs are ($QTDIR/bin and $QTDIR/lib/qt3 I suppose).
This one doesn't. It does build in Fink. I would use the Fink version, but I don't feel like having two redundant QT's. Evolvotron needs the source directory of QT in order to build, and the developers of QT consider that behavior to be correct. By their standards, the MacPorts installation of QT is deficient. I know almost nothing about QT and this was my first attempt to write a portfile. If anyone else wants to try, I can upload what I have.