Hey Cameron,
2. Use 'license fields' to enable features of my SDK.Checking each feature using this method is straight forward, where this becomes really complex is enablingusers to upgrade or even downgrade their features from a store. The store would have to find the activation using either email, or the activation-key, and change the 'license fields' representing the feature set.That is could get complex in a store, and I would like to avoid that if possible.
This is the best way to do it. Also, it'd be easiest to just prompt the user in your store for their product key (that way you can make the appropriate API calls easily).
If you have any specific questions about it I'll be glad to help.