ASP Server 4.0.2 can not be installed on top of Sun Application Server. It has to be either Sun web server 6.x or apache 1.3.x/2.0.x.
If you need both appserver and asp server functionality, you should consider installing webserver+asp server on a separate machine(the same one will be ok too) and use passthrough/load balancing plugin setup on a webserver to redirect appserver related quiries to your appserver.
One other note, asp server 4.0.2 is not supported on RH 4.