when USEing kde, the ebuild script should build kflash.kss and install it in /usr/kde/3/bin (according to the README
it seems that gplflash supports only qt-2/kde-2 (i get really many compile errors if i try to compile gplflash with kde support).
The last version (which we have) of gplflash is from June 2000, so it can't support kde3. It uses internal copies of libjpeg and zlib, too. Ugly... Well - the ebuild has no actual support for KDE (no dependency and it doesn't try to build the kscreensaver module by itself), and I think we should keep it that way. We're waiting for the kde 3.1 release, it's a bit late in the day to add support for kde2 stuff :-) Of course, we could mail the author asking whether there will ever be a new release, etc.
...but I don't feel like doing it, have no interest in gplflash myself. If you want to enquire about kde3 support in gplflash (and whether it's still alive at all), do so :-)