I dont know whats the configuration of the linux box u are using. If it is too slow - just soup it up - add more memory :)
But in linux doing ps shows all the threads too with the same amount of memory usage. This is normal for linux. There has been plenty of discussion about this if u just look around.
I only have 38 threads running on my 7.1 RH Penguin after starting jBoss/Catalina.
It's slow on my linux box too. What are the minimum requirements to run JBoss on Linux? I am using a 466 MHz Celeron, 312M RAM.(Just for development) It took 43 seconds to load JBoss/Tomcat up. And the http://localhost:8080/jboss pages load very slow.