You haven't stated any real requirements, other than being able to view XML with a stylesheet applied without modifying the XML to specify the stylesheet.
You could write a simple Java/C#/PHP/whatever application that reads the XML and parses it, creating either a DOM object or a JAXB class hierarchy, does the same with the XSL, applies the transformation and writes out the transformed XML. You can then view this in an appropriate viewer (that would be a function of the transformation -- typically it would be a text editor, a web browser, it could be PCL that you feed to a printer, anything really).