What elements need to be present for an open source project to be successful (And really what is success?) Recruiting pipeline is critical, participation is essential to life of the project. Eclipse/Sage/Octave/Blender/MySQL/Fedora/Linux/Apache/Firefox/Handbrake/VLC. Give up power early, let more people participate in the project as early as possible. Advertise the on-ramp for your commiters/contributors clearly. A license that is compatible with the target audience (GPL,LGPL,BSD,MIT).Re-use of existing technology to get going quicker and not re-invent wheels.
What does the path to development entry look like? Need to collect some stories from people who come into a developer community and are still with it (example of the Redhat Interns who started at mid-teenage years). For the classroom experience Inquiry/Active/Constructivism style learning on open source projects is a good start. Providing an outlet for creativity is another path.
What does small scale Community Architecture look like? (still open question) OS project managers need to look at the contribution pathway, lower barriers, maximize visibility not just of the project and the transparency of the processes, roadmaps.