As the query is about licensing, you can call 1-800-426-9400 (select option 4), Monday through Friday, 6:00 A.M. to 5:30 P.M. (PST) to speak directly to a Microsoft licensing specialist. You can also visit Microsoft Volume Licensing Site
http://www.microsoft.com/licensing/ to find the contact information.
Regarding System Center Essentials 2010 Licensing, I would like to share the following document with you for your reference:
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