Beyond immediate contributors, the strength of a project's community is evident from ecosystem projects that extend and are built upon them. This demonstrates that the core project community alone doesn't always tell the whole story of a project's momentum. Looking more broadly at the ecosystem can further describe the overall success of an individual project.
Notably, Backbone has a substantial ecosystem, showing its overall momentum and usage in the industry. In an effort to further validate the Backbone ecosystem, I filtered my search to include only Backbone-related projects that have three or more stars on GitHub, which resulted in 1,627 projects. Compare this with 794 AngularJS projects with more than three stars, and Backbone's ecosystem is still two times the size of AngularJS's.
Because the full-stack solutions have a different scope than many of the other projects, I wanted to take a separate look into their growth. Full-stack solutions include both a client framework and a server-side framework; hypothetically, the amount of code involved should be greater, as should be the number of contributors participating over time. The chart indicates each of these projects is in a relatively early stage with moderate participation.
Lines of code and commits
You may be left wondering about the size of the code bases for each of these projects -- and the relationship between that number and the number of contributors. Comparing these, we see that community size and total commits have little correlation to the size of the code base. For example, AngularJS shows a ratio of 413 LOC per contributor while Ember shows a ratio of 146 LOC per contributor.
You can, however, correlate the size of the community (all-time contributors) with the all-time number of commits and see that the number of commits per contributor varies greatly by project. This may show that some projects are easier to contribute to, affecting their long-term sustainability.
Reading the tea leaves
Community size and growth are important indicators of a project's momentum. While these indicators can't tell us the whole story, they provide important insight into projects that are being heavily invested in and help us make decisions based on the viability and sustainability of the community behind a project. They can also aid us in finding tipping points in a project's life span, providing us with opportunities to both engage in projects and influence change.
The subject of rich UI frameworks is near and dear to me, as I spent five years at Adobe driving product marketing for the Flex framework, now an Apache project. Based on all the data analyzed here, my take is that Ember and AngularJS are emerging as the frameworks to watch. That said, the ecosystem surrounding Backbone demonstrates both the popularity and commitment to this UI approach, and is therefore sure to have a continuing, bright future ahead.