OS4 does not run Apple Java (or any Java version), so it is not susceptible to this.
As for legacy Amiga viruses infecting the NG platforms, I suspect it is doable in some form. But as to how badly they would effect you on modern hardware is another story. Things have changed a lot in the ways those old viruses would bugger up a system, and a fair number of them looked for specific hardware to corrupt specific devices. A 68k Amiga virus meant to do bootblock floppy infections won't do a hell of a lot on a a OS4 machine, etc.
The legacy Amiga viruses were coded just to hassle the user, or as a proof of concept and don't have much threat in the modern day, rather than to steal your identity and pass it off over the internet like it is now.
Modern virii and malware just convert your machine to a botnet service, or work to gather your personal information.
If anyone has an old collection of Amiga viruses, I'd love to get ahold of them and see what they do exactly on my SAM 440.