You could create an identity system, where users can create personal accounts and have projects, similar to github. Maybe you should simply use github, that way popular projects would keep their well known names.

Do not hustle with email, install a system to handle MX records by the user, maybe with an interface that has some defaults (github, gmail).

After that create an OAUTH provider. Now you can provide other services through partnerships. I would not give away the ability to define custom sub-subdomains, instead let them choose between different service providers for predefined subdomains like these:

* forum.project.js.org

* news.project.js.org

* issues.project.js.org

* mailinglist.project.js.org

Create a skin-able overview of all the services at project.js.org. For the beginning you could simply pull in githubs README and add a navigation bar at the top. Later you could create something more dynamic.

Host an aggregator for each service at:

* js.org/forum

* js.org/news

* js.org/issues

* js.org/mailinglist

After you successfully created an enormous community and locked everybody in, turn evil, go into profit mode and add:

* jobs.project.js.org

* donate.project.js.org

* sponsors.project.js.org