The Granular Restore Option (GRO) is included at no extra cost for both BESR & BESR SBS.
The Management Solution (BESR-MS) is now free and can be downloaded here: https://www4.symantec.com/Vrt/offer?a_id=88724. This will work with the SBS version as well as the standard server/desktop editions of BESR.
You can just download BESR-SE (server edition). As you say, it's the license key the determines whether or not you are using the SBS edition.
In terms of how many servers you can install the SBS edition, I'm not sure about that. I would suggest you contact customer care who should be able to answer that:
http://www.symantec.com/business/support/assistance_information.jsp
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