While it is not advertised much on their own site Overleaf is AGPL3 licensed and is mostly open source: https://github.com/overleaf/overleaf https://github.com/

While it is not advertised much on their own site Overleaf is AGPL3 licensed and is mostly open source: https://github.com/overleaf/overleaf https://github.com/overleaf/overleaf