Although WDB is originally developed and hosted by met.no (http://www.met.no), it's a true open-source project under GPL2 license. If you would like to contribute, contact us using the mail address listed in the sidebar.
We are currently working on setting up a public mailing list that will be utilized for future development discussions.
There are many ways to join the project, either by writing code, or by testing and/or helping to manage the WDB Issue List.
Before you contribute code, you might want to read: