Hi,
I'm CEO at Opens and leader member from SNEP (http://www.snep.com.br).
SNEP is an Soft PBX based on Asterisk but build from the ground. We have more than 40.000 servers running in Brazil.
SNEP is licensed by GPL but was projected as a Ecossystem and not just a Software Project.
This means that it is sustainable for everyone on the ecossystem: founders, developers, manufafturers, service providers and users.
The main model said: "Do what you do best and keep the rest with the ecossystem!"
This means you need to known what you do best and recognize the work of others that support your business.
SNEP is modular, that allow anyone developer your own module easily and create your own solutions combining modules from anyone who want share your work and business.
Keeping the project walking together, without forks, all grow together!