All our plugin’s are built to work on a WordPress Multisite installation (e.g. each site will have an own Real Media Library folder tree). So yes, you can activate the license in a multisite installation.
But you have to give attention on the licensing model itself. Due to the fact that a plugin can be uploaded network-wide you only need one purchase code – but this is currently not correct. You need to purchase one license for each thematic website. For example:
example.comonly needs one license because it is associated to each other
product2.example.comneeds two licenses because it differs from thematic