Update README.md

Author: seidewitz

README.md

@@ -34,7 +34,7 @@ associated files [Common-Public-License-1.0.txt](https://github.com/ModelDriven/
 
 The implementation build requires the following to be installed:
 
-* Oracle Java Version 8 or above - see http://java.oracle.com/
+* Oracle Java Version 8 - see http://java.oracle.com/ (currently cannot use JDK 9 or higher)
 * Apache Maven Version 2.2 or above - see http://maven.apache.org/
 
 To build from the command line: