We've talked about this idea within Lombiq for quite a while and it's finally here! The DotNest SDK is the easiest way for developing themes for DotNest sites before deploying them as a Media Theme. It contains the same Orchard code base and all the open-source modules and themes on top of that as what's running on DotNest, so you can run your site locally with confidence that it's going to behave almost exactly the same as the live one. We also have a nice developer story with automatic updates from the SDK to your repository to make sure that you're able to work the latest code (make sure to read the Readme!). The DotNest SDK is available as a Git repository on GitHub and as a Mercurial repository on Bitbucket with continuous bi-directional synchronization powered by Git-Hg Mirror, another awesome Lombiq project.