Why should this be included in the repository? Already in source, but as an empty dir (https://dev.getsol.us/source/qt5ct/). Essential tool for qt5 tweaking (aka "making apps not look like w95" in non-Qt DEs)
Is it Open Source yes, https://sourceforge.net/p/qt5ct/code/HEAD/tree/trunk/qt5ct/COPYING
Who and how many users do you anticipate will use this software? Most users of non-Qt environments probably.
Link to source tarball/zip file https://sourceforge.net/projects/qt5ct/files/qt5ct-0.36.tar.bz2/download