eXist has been founded by Wolfgang Meier (wolfgang at exist-db.org) in late 2000, after reading a bunch of articles about efficient indexing methods for XML during his summer holiday. The project has been continuously developed since then. Wolfgang is still project leader and the main core developer of eXist.
The original plans have changed quite a bit over time, mostly in response to user demands. For example, while the main focus of eXist has been on document-centric documents in the first place, updating documents via XUpdate has become a major topic recently as more and more data-centric applications were developed with eXist.
You are welcome to contribute to the future development of eXist. If you would like to get involved, the first step is to join the mailing list. You may also have a look at the roadmap to see the known issues that need to be addressed.
Check Building eXist for documentation on how to access the subversion repository. To become an active committer, start to post patches to the mailing list. You will get write access to the Subversion repository if your patches are ok.
The following people have contributed to eXist (by writing code or supplying patches) or are active committers (in strict alphabetical order):
(probably, some names are missing here, please send a message to Wolfgang to complete this)