Windows 2003 CAL requirements

I have one box running with 50 CALs in place.

I plan on getting a second win 2003 box to run “Enterprise Search Express”,

http://www.microsoft.com/enterprisesearch/serverproducts/searchserverexpress/default.aspx

On my second box, do I need to purchase another 50 CALs? Users connect to Enterprise search via a browser. Are CALs required for this purpose?