That has very little to do with this particular attack. The NSA did not attack the proprietary code, which uses standard, open, and publicly-known and documented cryptographic operations, by the way. They compromised the key custodians.
While I agree in principle about open source, using purely open-source software would not have provided any defence here.
> While I agree in principle about open source, using purely open-source software would not have provided any defence here.
In open source software / hardware there wouldn't be "master key" that can't be changed and that have to be used by telecom's. Yeah of course no doubt NSA may penetrate in network of every of them, but it's would be a lot more costly.
Any architecture that requires pre-shared symmetric keys is going to have this problem. The fix is architectural, not open sourcing stuff. From what I understand LTE is significantly better.
While I agree in principle about open source, using purely open-source software would not have provided any defence here.