CMake Warning at b/slicersources-src/CMake/SlicerBlockFindQtAndCheckVersion.cmake:22 (find_package):
By not providing "FindQt5.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "Qt5", but
CMake did not find one.
Could not find a package configuration file provided by "Qt5" with any of
the following names:
Qt5Config.cmake
qt5-config.cmake
You can already run Slicer on tablets, see for example here (running on Surface Pro). If you want to use specifically an iPad then you probably just need to wait a bit - soon you’ll be able to run the same applications on your Apple laptops and tablets.
If you benefit from using Qt then it is nice if you contribute to its development by buying a commercial license, but this is not required. You can use Qt on iOS with free LGPL license as long as you make it possible for users to replace Qt libraries (see explanation here).
If you have further questions, I would recommend to continue the discussion on the Slicer forum, as this topic is mostly about 3D Slicer and not VTK.