KDE makes the most current—the "bleeding edge"—source code available for anyone to download and test. This is good for the project because exciting new code can entice developers into coding for the project, and the sooner code is available for testing, the sooner bugs can be reported and fixed and feature requests can be made.
You can access the CVS source code via the WWW, cvsup, cvs, or by downloading snapshots from an FTP site. Only cvs requires an account because this method can also allow you to write to CVS. Each method has its advantages: the WWW interface is convenient for browsing files and logs; cvsup lets you stay up-to-date with minimal download time; cvs also lets you stay up-to-date with minimal download time, but lets you make changes to the CVS; and the snapshots offer a convenient method for occasionally downloading the development version of KDE.