Simply and rudely put Darwin and DLU don’t want to work with you. Ion doesn’t even have developers. And also a quote from humanoid because why not

“More people doing something on the same thing does not automatically result in faster progress, especially if those people have next to no experience but “want to contribute something anyway” (in which case it ends up having the exact opposite effect).
We don’t want to give the impression that we are “elitists” but we prefer to keep the organization of our project in a controllable manner so sharing the source with other people is not an option for us at the current point in time.”