Wow, just wow. While animation isn't my foray it sure looks like a lot of time and effort has gone into Subdiv only for them to give it away and let you use it for anything. Pixar are amazing and not to mention the end result of Subdiv is as equally as amazing.
Perhaps even more promising is the effort they appear to be putting in to maintaining the open-sourced project.
Obviously Pixar is still using this library, and would love to get fixes and features to fold back into the upstream project, however they are also actively managing and responding to issues being raised. This speaks volumes to how serious they are about supporting this software in its open-source form. I hope this becomes another successful case study of how to do open source, and provides useful feedback and additions for Pixar.