Hello, do you plan to create some modern look for this website? To look like website from 21th century? :) It is not hard, I would just use Bootstrap and it will look great + it will be responsive design. I can do it, is this page open source? Somewhere on git?
We had a custom theme, but when we updated the software, nobody volunteered to update the theme to work on the new version, so we went back to the default. The website is fairly standard Bugzilla. Code: https://cgit.kde.org/websites/bugs-kde-org.git/?h=kde-5.0 Documentation on making skins: https://bugzilla.readthedocs.io/en/5.0/integrating/skins.html
You probably want to contact Bugzilla upstream regarding this - my understanding was they were working on a redesign of the default theme (and asked us for the code to the one we used to have)
As Ben hints at, at we are planning to do this after some upstream changes. No need to track this here; it's already planned. :)
So I am looking forward to it :) I hope it will be responsive design too (for mobiles).