RouteConverter and Mac OS X

[routeconverter]

I did not read this careful enough. Does that mean the prerelease gives an error message when the java version is too low? <1.6 ?
Or does it give an error/warning message on java versions between 1.6.0 and 1.6.0_13?

It warns if the version is below 1.6.0_14.

Also: Is it then necessary to use the Java6Check.jar?

Yes, because that checks for older Java versions before 1.6 that cannot even execute RouteConverter since it's now compiled for Java 1.6.