Kdevelop 4 and kdevplatform beta6 .deb packages for Kubuntu Jaunty 9.04 are available on my backports PPA.
To install them:

• Copy the lines below and add them to your system’s software sources. (Read about installing)
  
deb http://ppa.launchpad.net/daniele.domenichelli/backports/ubuntu jaunty main
deb-src http://ppa.launchpad.net/daniele.domenichelli/backports/ubuntu jaunty main

• Import public key for my PPA:
  
  sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 9D0C02D0

• Update and install package kdevelop
  
sudo apt-get update
sudo apt-get install kdevelop


EDIT:
Also .deb packages for Kubuntu Karmic Koala 9.10 are available on my backports PPA.
To install them just follow the instructions for Jaunty, replacing the lines to add in your system’s software sources with:

deb http://ppa.launchpad.net/daniele.domenichelli/backports/ubuntu karmic main
deb-src http://ppa.launchpad.net/daniele.domenichelli/backports/ubuntu karmic main