Certified JVMs on Solaris

What does the cryptic line “webMethods does not recommend using JDK 1.3.x to compile because of behavior introduced in JDK 1.3.0” mentioned in the install guides from 3.X to 4.X B2B really mean?

Does it mean the server will not work or become horribly unstable or does it mean certain or rather specific compiled code will not work on 1.3x?

Most if not all of the code we have gotten from webMethods support in the past six months has been complied on 1.3 … and will generate the error :

Warning: The package or release Wm**** has been installed but has not been activated. The JVM version specified by this package or release
(1.3.0) is newer than what is running on this B2B Server. You can attempt to active this package in Package > Management > Activate Inactive Packages.

Why does webMethods not certify the 1.3.x JVM?
Their developers appear to use it …

Thanks in advance for any insights. - RC