The bill makes no mention of proprietary software or hardware.
The bill references Common Criteria certification procedures for the software running the network. This potentially could be used to exclude the use of custom operating systems and reconfigurations of, say, Linux or BSD, without them undergoing certification.
the intent is clear: critical private national infrastructure
means air traffic control and the power grid
Linux has been EAL4 certified under the ludicrously weak and pro-forma common criteria. You can sell to DoD, on the real DoD secure networks, at EAL2. The bill also doesn't require everyone to run CC-certified OS's.
