Just reading the release notes of the SED10.3 for OSX, it's saying there is a requirement for JRE to be installed, and if not itll autoinstall prior to installing SED. What is JRE actually for? Can it be removed after installation? I cannot see where JRE would fit within an installation of PGP, this isn't a requirement of the Windows version as far as I know.
I am surprised that nobody has responded to your question, so I will jump in.
It is my understanding that Java is required only for PGP installation. In the past, I had to install Java before installing PGP, and then afterwards I disabled Java using the Java Preferences in the /Applications/Utilities folder. Despite disabling Java, I did not notice any impact on the various PGP operations I performed - PGP WDE authentication at boot, mounting PGPdisks, encrypting files, and using cut 'n' paste for encrypted email.
I did not remove Java, I merely disabled it using the checkboxes in Java Preferences. Be aware that Apple removed Java Preferences from the latest versions of the Mac operating system, so don't be surprised if you cannot find it now.
Java is needed for token/smartcard support on Mac OS X. This would typically be used for access/security on an external drive as tokens and smartcards are not supported for preboot authentication on a Mac currently.