"At Spark, we’re making it easier to bring connected 
   devices to market with the Spark Core, our Wi-Fi 
   development kit, and the Spark Cloud, our cloud service for 
   connected devices."

I found SparkCore on github[0] and the C++ communication lib for Core to communicate with SparkCloud [1], but I did not find SparkCloud itself on Github. Is that component going to open-source as well?

It would be nice if you had the option to host your own cloud service. You could protect your business model at least partially by using an open source license that requires people to change the name if they decide to fork it and productize it, such as the Artistic License v2.

[0] https://github.com/spark/core

[1] https://github.com/spark/core-communication-lib