To download the Web Based System Manager client you simply open a browser window and type the URL http://<ip address of your HMC>/remote_client.html.
To check the version of your HMC, type lshmc -V
hscroot@localhost:~> lshmc -V
“version= Version: 6
HMC Build level 20070201.1
MH00985: Miscellaneous fixes for HMC V6 (04-15-2007)
The Hardware Management Console v7 has web access, so you don’t need to install a client to use it.