There's always going to be downsides and edgecases when granting any party a monopoly over anything. At least if it's limited to 2 decades any unintended consequences, philosophical objections, and etc are hopefully kept within reason.
Meanwhile, there are cases where copyright of more than 2 years is overkill.
I don't know what, but it seems like we need some sort of mechanism for variable-length IP duration is needed.
I could understand for medical devices maybe but even then it seems like the software is a tiny part of the overall cost of a given design. A competitor could already do a clean room reimplementation in that case.
But I guess it wouldn't be all that bad if there were a carefully crafted extension for government certified software that was explicitly tied to the length of the certification process.
If you do something that requires stealing the code (publishing it, selling it, etc) the company can legally fuck you up.
Now, once it's in tbe wind, it becomes almost impossible to pursue from a practical point of view, as any implementer can claim trade secrets to avoid showing you the code.
Also remember that the original point of copyright and patent protections is to encourage people to create the protected works in the first place but Boeing isn't just going to stop making aerospace software without copyright because their hardware will be useless without it. So if anything, any software that is needed for hardware made by the same company to function doesn't really have any right to be copyrightable at all.
I can't use SQLite for aviation even though it was certified.
I can't even claim FIPS compliance for my software without going through an expensive process, even though I only use FIPS approved primitives.
Building on certified/compliant libraries helps, but their vendors can certainly contractually make me pay for it.
All OSS libraries have a warranty disclaimer; using them according to even those licenses automatically excludes "fitness for a particular purpose."
Why would public domain software be any different?
The moat is the certification process, not the code itself. "I copied this from somewhere after it was already certified" might fast track something, but it's not gonna fly with "certification was good, done."
Consider if you will that if some guy were to fly a drone the size of a car that he knocked together in his garage over a residential area people would not accept that. Yet private pilots in cessnas fly over neighborhoods constantly.
I've always liked the idea of a Harberger tax-style patent enforcement fee:
The patent owner declares the value of their patent on an annual basis and pays 1-5% of that declared value per year for the privilege of relying on the government to enforce their exclusive ownership of the patent. At any point, another party can buy the patent at its declared value, which discourages patent-holders from declaring artificially low values. The annual fee discourages artificially high valuations for indefinite periods of time -- as the patent yields less return over time it makes less sense to keep paying a high annual fee, encouraging owners to lower the declared valuation or end the patent protection altogether when it's no longer profitable.
To discourage hoarding patents indefinitely one could either set a hard upper limit (e.g. 60 years) or increase the fee over time, for example every few years the fee increases by 1% until at some point the patent is effectively publicly owned.