Comment 1 for bug 1445782

I wish I could find you the links I was reading earlier. I'm paraphrasing and may have my details slightly off but some of the reasons you see what you see comes down to limited resources for testing new packages that go into each upstream/release, the freeze on packages that occurs for each release, the resources for putting the packages in for Kadu that fix security issues/bugs in existing releases, and probably some politics and policies thrown in there, etc.

Probably need to raise this in the bug area for kadu:
https://bugs.launchpad.net/ubuntu/+source/kadu

Or in Kadu's forum/the developer(s). They probably have more influence than an individual in getting the correct packages in Software Center.

As you said, the terminal isn't really for everyone, but on the other hand the instructions could also be improved from the website (my nice way of saying they are close to terrible for normal people):
They could explain that the commands go in the terminal, how to open the terminal, how to enter them, what to do about any error messages, how to know it was done correctly, etc.

"Sometimes in current Ubuntu version old Kadu can be available. If you want newset Kadu follow these instructions:
sudo apt-add-repository ppa:mati75/kadu
sudo apt-get update
sudo apt-get install kadu
sudo apt-get install kadu-external-modules kadu-themes
"

Not here to tell you what to do, but since you said Kadu is critical, and this is open source, maybe the developer would listen to suggestions from you on how to make it easier for normal users to install until the better packages are available. (Vivid currently lists v. 1.3-1).