I would like to know whether implementing portal in Jboss can cause major load to the server. For example, If you implement weblogic using portal the server needs to much memory. In the case of Jboss is the same?
This will depend very much on the overhead of the portlets you deploy and the volume of use you are expecting such as consurrent users and throughput of their requests.
I have JBoss Portal 2.0 installed on JBoss 4.0.2 using the default memory settings without the need to adjust them.