This article really seems to be about two different things:
* PHP/Java integration
* MantaRay JMS
Using PHP/Java integration by instantiating a JVM within the PHP cgi interpreter seems insane. The startup cost would be enormous. Since MantaRay is pure Java, you might as well just write a Java CGI.
Instantiating a separate JVM into each Apache process (pre-fork) seems every more insane. The JVM requires maybe 20MB at minimum, so creating a 100 instances (for a 100 processes, is also very expensive. Using one of the Apache 2 threaded modes would probably work best, since a single Apache process could serve multiple requests (reducing the process count and the number of JVMs created).
Why no dicussion about other JMSes? MantaRay isn't the only open-source JMS, and probably not the best. Since there is nothing PHP specific to MantaRay, ActiveMQ would probably be a better choice. And it could be used via the same PHP/Java interface (with all the same instantiation issues).
A native PHP client driver for a JMS server is really what is required in order to make JMS on PHP popular.