A browser-based planetarium that can be customized and embedded in web pages. View as full-window. Some examples with code excerpts and some unit tests.
It is provided as is. Do not expect support.
This project was made more than a decade ago because nothing quite like it existed on the web. Since then, plenty of other projects have been created. For instance, Stellarium Web Engine now exists and uses WebGL (which wasn't really a thing in 2010). Check if that is more suitable for your needs.
Stuart Lowe initially developed this at Las Cumbres Observatory (LCO is a private operating foundation, building a global network of telescopes for professional research and citizen investigations) between 2010-3. After leaving LCO in 2013, he maintained this in his spare time for several years.