This project is now abandoned in favour of MorganaXProc-III which implements XProc 3.0: https://sourceforge.net/projects/morganaxproc-iiise/
MorganaXProc is a full implementation of XProc: An XML Pipeline Language (W3C Recommendation 11 May 2010) written in Java, supporting all required and optional steps, the steps proposed on EXProc.org and also the document templating steps "p:in-scope-names" and "p:template".
XPath 2.0 or XPath 3.0 is used as expression language.
XSLT and XQuery are supported out of the box, while a flexible connector mechanism also allows to employ your favorite XSLT and XQuery processors.
The current version is 1.0.x. It is very close to the recommendation with all related tests of the XProc Test Suite passed.