The old documentation page on that URL is currently unavailable. But we are working on a new documentation page.
I don't think so. I am working on new docs for ISPConfig, when that is done we might add a developer part.
It is always officially in gitlab (https://git.ispconfig.org/ispconfig/ispconfig3/) and not github though there may be others who are keeping their own personal copies for own development in github.
I want to join development team, I have 8 years php experience and I'M using ispconfig for many years. I want to contribute. I registered to your git server, username is `kodmanyagha` Is it possible to join to your team?
