Main project page: https://emscripten.org
Chromium builder status: emscripten-releases
Emscripten provides Web support for popular portable APIs such as OpenGL and SDL2, allowing complex graphical native applications to be ported, such as the Unity game engine and Google Earth. It can probably port your codebase, too!
While Emscripten mostly focuses on compiling C and C++ using
Clang, it can be integrated with other LLVM-using
compilers (for example, Rust has Emscripten integration, with the
Emscripten is available under 2 licenses, the MIT license and the University of Illinois/NCSA Open Source License.
Both are permissive open source licenses, with little if any practical difference between them.
The reason for offering both is that (1) the MIT license is well-known and suitable for a compiler toolchain, while (2) LLVM's original license, the University of Illinois/NCSA Open Source License, was also offered to allow Emscripten's code to be integrated upstream into LLVM. The second reason became less important after Emscripten switched to the LLVM wasm backend, at which point there isn't any code we expect to move back and forth between the projects; also, LLVM relicensed to Apache 2.0 + exceptions meanwhile. In practice you can just consider Emscripten as MIT licensed (which allows you to do pretty much anything you want with a compiler, including commercial and non-commercial use).
LICENSE for the full content of the licenses.