The public header qaxselect.h includes ui_qaxselect.h. I don't know if other include problems exist. I noticed this one when testing if #include <ActiveQt> works. (Update: this part is now fixed)
The Qt CI system likely did not catch this as the install of Qt is not autotested at all. Tests are run against the build-dir. (See also
Also, the fact that headers are in the 'ActiveQt' directory instead of a directory prefixed with 'Qt' should be considered a bug that can be fixed for Qt 5.0. The porting script from QtGui/QWidget to QtWidgets/QWidget can probably be extended to help there.
qtactiveqt also does not follow other Qt conventions, as it does not use the qt_module.prf, and it represents multiple libraries instead of one. It should really be two modules - AxContainer and AxServer.