As established in my earlier comment, your original premise and your entire argument is incorrect. Akka is not a 'messaging platform'. It's a bunch of libraries

As established in my earlier comment, your original premise and your entire argument is incorrect. Akka is not a 'messaging platform'. It's a bunch of libraries that you link in to your JVM app. No one (well, no sane person) would try to 'charge others a fee to let them use Akka' on their server because technologically that doesn't make sense. It's akin to charging people a fee for a service to concatenate strings together. Hence as you can see, the SSPL is not an appropriate fit for Akka anyway.