Some clarification on what you mean would be great.
When I look at their organization on Github I see quite a few active projects e.g. "Sharq" - SHARQ Server is an flexible, rate limited queuing system based on the SHARQ Core library and Redis. (https://github.com/plivo/sharq-server) as well as client packages in quite a few languages.
Beyond that the documentation you referenced clearly points out that FreeSwitch (https://github.com/signalwire/freeswitch) is the telephony engine (https://web.archive.org/web/20130314113846/http://docs.plivo...) and the install script from the docs shows that their roots are in Pilvo being a Python web app (https://github.com/plivo/plivoframework/blob/master/scripts/...). I also see a few Django applications in their repositories as well.
Thus, they open sourced their software. Are they open sourcing all of their software? Likely not. It could be that they open sourced much of their code and then got no contributions.
If they weren't receiving any contributions in alignment with their development, there would be no value for them to continue to have that distraction from running their business. It could also be that they didn't have the resources to _maintain_ external facing repositories, issues, and the communities around them.
Providing a more clear explanation of your expectations would help get you the best answer.
