Review request for JMC-6619: Update to the third-party license readme

[Marcus Hirt]

Hi all,

Please review this update to the third-party license readme.

Jira:  https://bugs.openjdk.java.net/browse/JMC-6619
Webrev: http://cr.openjdk.java.net/~hirt/JMC-6619/webrev.0/

Kind regards,
Marcus