I agree with you. As far as I know Intel is not releasing the code for that service. Probably it is part of their strategy, but I could be wrong.
There are other platforms out there that have potential. Have you looked at the spark core or the upcoming spark photon?, they are open source and they have a server side as well.
Also, there is OpenHab. It works great but it is more geared towards home automation.
And I am sure there are quite a few other options out there...
There are currently no plans to opensource the backend of enableiot.com.