While the developers officially announce qt3 support, they do provide a way to build against qt4. In the README it states how. They try to keep their code to work with the qt3to4 provided upstream. And provide functionality in their make file. From what I can tell it works, the code compiles and the wizard for qbanking launches. (qt-3 isn't installed on my machine)
Created attachment 199973 [details, diff] aqbanking-qt4.patch Here is the patch to the ebuild. Pretty much bare bone changes made. I added the make qt4-port to the configure, 1) b/c i didn't want to re-write the stup compile, and it seems to still be configuring the package, at least in my head. This should still work with qt3, though I didn't test it, since qt3_libs and qt_includes would be empty. Might want to include a ewarn before the compile that if both qt3 and qt4 are selected, it would use qt4 by default. (or it should in theory)
Created attachment 204326 [details, diff] aqbanking with qt4 support aqbanking-qt4.patch with conditional make qt4-port and src_prepare section
Created attachment 204327 [details, diff] qbankmanager with qt4 support
Patch works for me, too, with Qt4 only installed and qt4 selected and with Qt3 and Qt4 installed and qt3 selected. Qt3 and Qt4 installed and qt4 selected does not work, because configure doesn't find qt3to4. Qt4 works, but translation is broken and several widget are badly themed, so the Qt4 version is no real alternative. I've attached a version of the aqbanking-qt4.patch with minor improvements and a patch for qbankmanager.
aqbanking-4.2.0 has USE="qt4" and +*qbankmanager-0.9.52_beta-r1 (13 Dec 2009) + + 13 Dec 2009; Samuli Suominen <ssuominen@gentoo.org> + +qbankmanager-0.9.52_beta-r1.ebuild: + Use Qt4 instead of Qt3 wrt #280127, thanks to Ryan and Arne Stäcker.
Please reopen this bug, because on a qt3-less and qt3support-less system, aqbanking does not easily install! The aqbanking ebuilds have a severe lack of proper USE flag checking on qt-packages! It definetly needs x11-libs/qt-qt3support WITH KDE USE FLAG, because only the kde useflag triggers qt3to4 to be installed (Which is utterly stupid and I never would have thought about that, took me to compare useflags with other people on irc to find out!). I am not quiet sure if more packages with qt3support useflag were needed in the process of getting it installed, I needed to set the qt3support useflag for qt-core manually, but that may have been related to something else. And the qt-qt3support package did not get automatically pulled in, but this is more a qt related bug then a aqbanking related bug.