Version 3.4 is binary compatible with previous 3.x versions and 2.0. There should be no changes required to existing binary code.
However, version 3.4 is not source compatible with 3.3.
The interface NtpV3Packet has been updated to add 3 new methods. Adding methods to an interface does not affect binary compatibility The clirr report shows which methods have been added. (note that the report does not distinguish between source and binary incompatibility) Code that uses the interface will need to be updated and recompiled. However code that uses the implementation class NtpV3Impl will continue to work as before.
Version 3.0 is binary compatible with version 2.0. There should be no changes required to existing binary code.
However, version 3.0 is not source compatible with 2.0.
Several obsolete/unused constants have been removed.
Also, some throws clauses have been removed from methods which did not actually throw them.
Version 2.0 requires a JDK 5.0+ runtime. It has also been tested on JDK 6.0. There should be no changes required to existing client code.
This version is a drop in replacement for NetComponents. Only package names have changed.