X4O is not a language but a framework to create other XML language implementations.
+X4O has an BSD style licence, to be compatible with wide range of software.
+X4O can write all parsing steps in xml debug output file.
To setup set the following properties before parsing a document.
+ TestParser parser = new TestParser(); + parser.setProperty(X4OLanguagePropertyKeys.DEBUG_OUTPUT_STREAM, new FileOutputStream(debugFile)); + parser.setProperty(X4OLanguagePropertyKeys.DEBUG_OUTPUT_ELD_PARSER, true); // optional ++
No, X4O had no built in xslt support.
+But you can implement an transforming language yourself with X4O.
+