I have come across many situations in which there is confusion as to what licenses are necessary, or required, when dealing with NetScaler appliances.  While doing some research into something else, I came across the following article in the Citrix website.  Its very apt title is Netscaler Licensing Dissected.  It is an excellent primer on NS licensing: it is concise, it covers everything there is to cover, and it is *accurate*.  Please bookmark it, or save it locally, and refer to it whenever you have questions related to licenses for NS appliances.
Netscaler Licensing Dissected