Donation and enterprise level support is what comes to my mind. Also depending upon what you are developing, running a training program could bring in some extra cash.
When you reach certain level on development, funds might also come in from bigger industry. But its tough to get funds upfront no matter what the source is.
May be you can look into what light table did - https://www.kickstarter.com/projects/ibdknox/light-table
Best analogy is knife vs swiss knife. AWS has a great toolset and comes handy when it comes to scaling, at the same time it seems complex if you don't know how to use it.