This bug is a tracker for those KDE3 apps that will not build when KDE4 is installed.
bugs #275733, #275969 too
Also broken: Bug 274737: games-mud/kmuddy-0.8 (Alternative: kmuddy-1.0 for KDE4: Bug 278506 ) Bug 248883: kde-misc/kdirstat (On my system 2.5.3-r1 fails with kdelibs-4.3.0) Bug 282829: sci-astronomy/celestia-1.6.0
Another one: Bug 248293: x11-libs/compizconfig-backend-kconfig For me the minimal patch (http://bugs.gentoo.org/attachment.cgi?id=190679) worked on x11-libs/compizconfig-backend-kconfig-0.8.2