There are three XSLT 2.0 processors currently available: Altova, Gestalt, and my own Saxon product. If you want a jar, then you must be using Java, so you should download Saxon from
http://saxon.sf.net/.
The XSLT processor that comes bundled with the Java JDK is Xalan, and it only supports XSLT 1.0.
Michael Kay
http://www.saxonica.com/
Author, XSLT 2.0 and XPath 2.0 Programmer's Reference