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Microsoft products can be licensed in two ways -by Subscriber Access License (SAL) or per processor (Proc). Some products are only licensed one or the other whilst other products can be licensed either. The essential difference is that a processor license allows unlimited users whilst a SAL is required for each unique user or device accessing the software. For products that allow either licensing model determine the cost under both models and opt for the cheaper one. Generally the larger the number of users the more economical a processor license becomes. Please see the individual SAL and processor FAQs for more detail.