We spent 3 months going door to door, making demos to people I knew were working on similar projects or looking for one. We had a good reputation in the ops and systems engineering community because of our work on dotCloud over the last 6 years. Then we bootstrapped the open-source community with that initial group of 30-50 people willing to federate efforts. By the time the project was leaked on hacker news, the github repo and mailing list were already very active.
Early members of that "seed" community included engineers from Twilio, Heroku, Soundcloud, Koding, Google, Meteor, RethinkDB, Mailgun, as well as the current members of the Flynn project.
I am flattered, but we are already well funded and are not currently looking for new investors. However if you're feeling generous I can point you to a few people who have been making awesome contributions to Docker on their free time. I'm sure they would appreciate donations, or perhaps contract work :)
There are also several startups currently raising money for a business based on docker. This is bigger than any one company!
Early members of that "seed" community included engineers from Twilio, Heroku, Soundcloud, Koding, Google, Meteor, RethinkDB, Mailgun, as well as the current members of the Flynn project.