That would be unfortunate as practically you’d go a long way if you can convince just the most popular feed providers.
What if you put down a clause that you open source a major version upgrade one year (or some other time period) after its release?
So the November code should be open sourced next November. Code written between November and May 2016 for requested features should be open sourced May 2017, and so on.
It would take a large investment for anyone to try replacing you, which won’t make it cheaper for Nu.