Yes, there will be an off-cloud release of Rocket. The Helix App Cloud is intended to make it easier for Application Developers to build their applications. We recognize that traditional embedded developers may want to build and deploy locally.
Instructions on how to do this are forthcoming. In the mean-time, you can download your project locally from inside Helix App Cloud by doing File > Download Project. You'll notice that many of the files have the Apache 2.0 license on them which means that you could preserve and maintain your project for 20+ years.