I am looking into Activesync for a project we may working on later later this year and am not clear now these technology is both licensed currently and how it will be licensed in the future.
Some documentation seems to be available on Microsoft Open Specification Support Team Blog and other places yet there is no SDK for AS at least publicly. Also there is mention of companies like HTC and Apple licensing AS. Does that also infer that they are paying for the license?
What you are looking for is the document Exchange_Server_2010_License_Agreement.pdf which can be found on this page: http://www.microsoft.com/openspecifications/en/us/programs/other/default.aspx
There you can see, that you have to pay for every sold piece of software that implements the Exchange ActiveSync protocol.