Wolfgang Meier has released eXist 1.0.1 and 1.1.1. "eXist is an Open Source native XML database featuring efficient, index-based XQuery processing, automatic indexing, extensions for full-text search, XUpdate support, XQuery update extensions and tight integration with existing XML development tools. The database implements the current XQuery 1.0 working drafts, with exception of the schema import and schema validation features defined as optional in the XQuery specification." The two version differ primarily in the indexing scheme used. 1.1 should be faster and not have document size limits. It's more bleeding edge, but 1.0 is quite a bit too limited for my tastes.
eXist is probably the major pure XML open source (LGPL) native XML database. However, whether it's ready for production use or not, and how large an application it can support, I don't know. I tend to doubt that it's the equal of DB 2 9 or Mark Logic, though I'd love to be proved wrong about that.
