Here are some important things to keep in mind when you consider contributing to the CKEditor project.
The CKEditor core is built of many .js files, each one corresponding to a class or a specialized object implementation. It helps us to organize the code better.
The source code is (or should be) well-documented, and clearly written, to enhance readability and make it easy to understand.
On the other hand, in real usage all that code must be downloaded and interpreted by the browser. This could make the software slow and the users angry.
This is not a problem, however. For the end user the editor code always runs in its compacted, single-file form. It is the original code processed, without comments or indentation. Even variable names are changed.
For a better coding style remember about the compression and familiarize yourself with CKPackager, the software used for compression of CKEditor.
All development should always be done on your local copy of the SVN trunk, or one of its branches. If you want to contribute some code, take time to familiarize with SVN. It is a powerful tool, and a central feature in the project development.
This project is made of people that have something in common: a passion to discover and to learn. Feel free to exchange your thoughts. People will love to think together with you.
This is the most important thing. Open source is a lot of fun... enjoy it!