If you are willing to help KDevelop, there are multiple ways to contribute.
If you want to help KDevelop with patches or new plugins, we are more than willing to help you get your feet wet! Contact us on #kdevelop on Freenode IRC, or drop us an email on our developer mailinglist. If you already have a patch, please post it on Review Board. If you are looking for bugs to squash or ideas for new features, try to look into the KDevelop bug reports on bugs.kde.org.
We are also desparatly looking for people proficient on non-Linux platforms, most notably MS Windows and Mac OS X. KDevelop can be built on these platforms, but there might be bugs. Especially on Windows there are some outstanding issues. We would very much appreciate your help, just contact us to get started.
Localization of KDevelop is handled by the awesome people behind l10n.kde.org. Please get in contact with them and start translating KDevelop. To check the translation status of KDevelop into your native language, please take a look here.
So far, KDevelop has not much documentation, if any. We are in desperate need of help here. Please step up, contact us via IRC or the mailing lists and start writing documentation. It is as easy as writing a short text and adding some screenshots to the KDevelop Documentation Wiki.