https://x.com/GrapheneOS/status/1906026235936813197
There are currently 10 developers paid to work on GrapheneOS (some full time, others part time) and 1 more that's in the process of being hired to work on it. There are few contributions made by volunteers other than the 1 person we're in the process of hiring since we hire them.
You can see what people contribute to by checking the repositories of the project. Each project member is free to have their profile private or public. People can and have used people's GitHub profiles to brigade issues they're participating in. Leaving it public makes that easier to do.