SgtSurehand That said, the developer of DivestOS recommends that people run GrapheneOS if they have a supported device.
Also, not really sure what you mean re: open source. All of GrapheneOS, including the apps it bundles are open source and permissively licensed.
To answer @pappadam's question, I'm not exactly sure whether LineageOS makes their apps available outside of the OS itself, but if they do, you should be able to install them just like any other app.