Eclipse Theia

With Theia you can develop one IDE and run it in browsers or native desktop application from a single source. Theia is designed in a modular way to allow extenders and adopters customizing and extending every aspect of it. Composing a custom IDE-like product is as easy as listing all needed extensions in a package.json file. Adding new functionality by implementing your own extensions is easy, too and provides all the flexibility you need.

Unlike other "open-source" projects, projects like Theia that are hosted at an Open-Source Foundation are protected against single-vendor decisions against the interest of the diverse community.