WebMolKit is a cheminformatics library that I’ve been working on for a long time: it runs on all kinds of JavaScript engines (browsers, desktop via Electron, command line via NodeJS). Its flagship feature is a powerful chemical sketcher, but it also has many supporting functions for handling molecules. As of now, the licensing terms have been switched to Apache 2.0, which basically means you are allowed to use it for non-open projects, as long as proper credit is given.