This tools is required for cross compiling kdoctools https://build.opensuse.org/package/show/home:rhabacker:branches:windows:mingw:win64:KF547/mingw64-kdoctools and therefore installed. obs has KDE4 and KF5 packages side by side
On opensuse there are the cross compile helper packages
both containing docbookl10nhelper and nothing prevents them from been installed in parallel
Nothing says that both must be installed at the same time. Just add conflicts to these packages against each other, so it is clearly marked that they are not coinstallable.
Furthermore, as already mentioned in D17650: Install kioslave.exe as kioslave5.exe under Windows, just focus the efforts on KF5 stuff, instead of wasting work to make umbrello & alkimia dual Qt4/Qt5, and adding more features to a stable Qt4 branch (4.8) of kmymoney.