And, zooming out a bit: the reason Hyperbola wanted to modify Rust / Cargo was to prevent it from being used to compile non-free software ("[we wanted] to have Cargo removed as otherwise non-free packages could be used from projects being compiled").
This feels misguided. If you're in the position of adding limitations to software or stripping out features to keep the user from using it with nonfree software, you've lost track of why that software freedom mattered in the first place.
No? The point is to keep the user's system free of non-free dependencies. As a user, I don't want to audit the several hundred packages that a single Rust application might decide to pull in; I'd prefer if such a thing were enforced instead. Otherwise, you might as well go use any of the hundreds of non-free distributions out there.
The Rust/Cargo license is also terrible grounds on which to build a free system anyway.
... Not sure if such modification is not incompatible with GPL family of licenses, though, but I am not a lawyer (you're not allowed to combine GPL-licensed product, whether v2 or v3, in ways that create derivative works whose parts are licensed with more constraints than enforced by the GPL, with special carveouts for AGPL)
Guix does the same per every Rust crate AND with Golang. You can support them by importing them with 'guix import' and checking the manifest.scm of every package for licensing reasons.
So do Trisquel and Parabola, but in a more radical way. No PIP, no Cargo, no nothing. You are on your own.
Whether one agrees with it or not, explicitly removing non-free software or the mere suggestion to install non-free software has consistently been a FSF litmus test for about twenty years in order for them to label an operating system as "truly free". Leading to exchanges such as the following in 2007 when Stallman remarked that he could not in good conscience recommend OpenBSD as their ports collection had wrappers that would allow the user to install non-free software more easily:
Key part: "Since I consider non-free software to be unethical and antisocial, I think it would be wrong for me to recommend it to others. Therefore, if a collection of software contains (or suggests installation of) some non-free program, I do not recommend it. The systems I recommend are therefore those that do not contain (or suggest installation of) non-free software."
"...problematic trademarks". Say what? There is a link: https://wiki.hyperbola.info/doku.php?id=en:philosophy:rust_t...
Follow that...
Really? Yougottabekiddingme....