A JVM (Java Virtual Machine) is a requirement for this modification as the pJIRC is coded in Java and the JVM runs the java application (as is the jIRC client which was an earlier (and non-free) choice for this mod's integration file).
The FlashChat that I mentioned also requires a 3rd party program to run (well 2 if you include the $5 flashchat application) which is the Adobe (formerly Macromedia) Flash Player. There is currently no FlashChat integration file available.