DreamFactory 2.0 will support API versioning where you can pass in the API version as part of the API call.
For now, my suggestion would be to set up one app (i.e. one API key) and have two services (or N services as you change features of the API). Make sure you never remove the previous versions of the API in DreamFactory. When you release a new API, update the app binaries to point to the new API. Old clients still point to the old API which you haven’t removed from DreamFactory. New clients point to the new API in DreamFactory. Both new and old clients use the same API key…but that’s fine since old client binaries point to the old API and new client binaries point to the new API.
This is a workaround for now. As I mentioned, 2.0 will handle API versioning in a better way.
Also, what is the API you are using? If you’re connecting to a remote web service, then having multiple API versions makes sense. However, DreamFactory’s auto-generated APIs for SQL, NoSQL, and file storage will be backwards compatible, so you don’t need to version them.