http://hashbangbash.com/downloads/slackpkgs/kde4.0.0/
check it out, and tell me where it breaks. i can not be responsible for this breaking any kind of your install, but if if does, do tell 😉
this is very, very, to me. on my wife’s laptop, it boots to a kdm console, where you can choose your session like normal, and kde4 is an option now!! and kde3/qt3 never have to get uninstalled.
vb
2008-10-28 UPDATE
i have moved these packages to http://cardinal.lizella.net/~vbatts/kde4-coexist/
cheers ! and happy hacking