How to manage IP with proprietary and open source components on an online platform

I am an engineer based in Sweden. I am developing a platform for browser embedded CAD visualization. The platform will be functioning with a server-side application that is proprietary and basically reading the user input in the form of CSG scripts, and then producing the output for the OpenGL viewer in their browser. The development for the modelling scripts will ideally be done in a GitHub-like environment with a broad community base of independent script developers.

So with one proprietary component (server-side software application) and one "open source" component (user-developed scripts via GitHub/GitLab-like platform), how do I manage the intellectual property the best? For instance, how much influence can I have over the user-generated content? How do I protect my own application the best? Thanks for your advice!