i have read in this forum that someone mentioned it can be done using some plugin that treats servlets as COM objects...... maybe try to serach this forum. sorry i dont know more than that (i thought it wasnt possible).
Also, you can use IIS as a front end web server and connect it to the HP Application Server through a Load Balance Broker (LBB) that will, well... balance the load... between however many application server instances you're running. For more info, check out the Administrator's guide: pg. 64, Using Web Server Load Balance Brokers