I plan to make a webapp but I don't want to host it myself so if people want to use it they will have to host it themselves. The source will be on GitHub and I don't know which licence to choose.
My requirements are that people are allowed to fork and modify the app but they should make pull requests on my repo for the modifications they do, so my app gets improved (not mandatory but I'd prefer).
The main problem is that I allow people to host the app but for private use only: I don't want to see a public website featuring my app appear with a different name etc.
In other words, the code is public and people are encouraged to enhance the app (by making pull request on my repo) but they cannot make their own website using my app (I want to be the only one to have this permission, if one day I decide to host the app myself).
For example, it's like if the YouTube website was on GitHub, people can download and host locally, etc, but they cannot make a public website using the app (for example ToTube.com).
So which licence should I choose to do so?