The correct libertarian position is the abolition of IP entirely so that you destroy the market for proprietary software. If you still have some draconian FCC type organization controlling light (which is still insane, and should also be immediately abolished by any libertarian administration) you could at least mandate that the radios be open source at all levels to enable citizens to verify conformance.
You could probably do an easier job forcing open source just by requiring all government contract hardware / software to provide you with all design schematics and sources that you then immediately publish for consumers to utilize. Without IP bullshit, once someone is publishing it, you can trust it if you personally verify it securely.
To be picky, there exists no market inherently for proprietary software, only a market for software in which the only way to keep the price above zero is to use artificial scarcity via "IP", DRM, and secret source, etc.
So anyway, the correct software freedom position (what Purism is at least claiming to support) is bigger and independent from libertarianism, so if we were to have the optimal legal framework, it needs 3 things: abolish patents and copyright (not trademark though), mandate source release for published works, prohibit DRM.
You could probably do an easier job forcing open source just by requiring all government contract hardware / software to provide you with all design schematics and sources that you then immediately publish for consumers to utilize. Without IP bullshit, once someone is publishing it, you can trust it if you personally verify it securely.