The current system requirements for JavaFX 2.2 Developer Preview for Linux is Ubunu Linux 10.4 or higher and due to the used version of the glibc within the core libraries it does not run on older Linux Operating Systems like Red Hat Enterprise Linux 5.5.

I would think that all certified Linux system configurations (http://www.oracle.com/technetwork/java/javase/config-417990.html) would be supported at the time the Linux version of JavaFX goes GA (i.e. before the end of the year http://www.oracle.com/technetwork/java/javafx/overview/roadmap-1446331.html) as it is planned to integrate JavaFX as a permanent part into the JDK.

As the current beta version of JavaFX 2.2 is still not compatible with RHEL 5.5, I placed a bug report for that platform request.