The animal exploitation industry (vivisection, slaughterhouses, zoo's, and so on) is a party, that is not yet selectable as module.

The term "copyleft" has appeared in Tiny BASIC, but without any actual meaning.
The term was then suggested by Don Hopkins to Richard Stallman. The first copyleft license ever written was the Emacs General Public License, but was never actually called "copyleft".
The intention behind copyleft is explained in the GNU Manifesto as follows:

GNU is not in the public domain. Everyone will be permitted to modify and redistribute GNU, but no distributor will be allowed to restrict its further redistribution. That is to say, proprietary modifications will not be allowed. I want to make sure that all versions of GNU remain free.

So, there are two keywords: free and proprietary. As for free, Stallman has clarified he did NOT intend copies of GNU to have to be given free of charge and that by "free" he only meant as in freedom. He thus regrets referring to GNU as free in the original announcement without clarification. So, here, "free" means "free software".
What does "proprietary" mean? According to GNU:

Proprietary software, also called nonfree software, means software that doesn't respect users' freedom and community. A proprietary program puts its developer or owner in a position of power over its users. This power is in itself an injustice.

I am not trying to discuss whether it's indeed injust, it's not my point at all, please don't assume my position on this (which either way is completely irrelevant), nor am I asking to agree with GNU. I quoted it simply to see what they mean by "proprietary": the first line explains it: "proprietary" simply means "not free", thus every program is either proprietary or free by definition.

Let us now finally go back to the definition of copyleft according to GNU:

Copyleft is a general method for making a program (or other work) free (in the sense of freedom, not “zero price”), and requiring all modified and extended versions of the program to be free as well.

So, copyleft is:

1. A method (not a specific license in particular).
2. To make any (copyrightable) work free (as in "free software").
3. To require modified copies to be free as well.

This is not the first occourence of the word "copyleft", however:

1. It absolutely is the first definition of it, Tiny BASIC never ever defined it.
2. It absolutely is the first popularized definition.
3. It absolutely is the current definition, how the word is currently interpreted.

Some sources defining copyleft:

• GNU: https://www.gnu.org/licenses/copyleft.en.html
• Opensource.com: https://opensource.com/resources/what-is-copyleft
• Wikipedia: https://en.wikipedia.org/wiki/Copyleft
• Copyleft.org: https://www.copyleft.org/
• P2P Foundation: https://wiki.p2pfoundation.net/Copyleft
• Oxford Dictionary: https://www.lexico.com/definition/copyleft

There are other reliable sources for the definition of "copyleft" as well.

Given the above, it's clear that the definition of "copyleft" is not ambiguous.
For a work to be "copyleft" it is a requirement that it is first "free".

Because works under the Hippocratic license are, by definition, proprietary (or at least not free in the same sense that it is meant when defining copyleft, see:https://www.gnu.org/licenses/license-list.html#hippocratic), they cannot be copyleft.

This is not one case in which there is a lot of ambiguity: there is none, in fact. The term "copyleft" has a clear and simple definition: it's not just about "trusting" GNU, which coined such definition, it's not just about trusting the GPL, which is by far the most common copyleft license. The mentioned definition of copyleft is extremely well accepted.

Of course, words are words, and they can be defined however one wishes.
However, there is no need to. It's confusing, it's unnecessary and it's kind of lazy.

The project is using the word "copyleft" incorrectly in the same sense as any other word can be used incorrectly.

I hope this issue doesn't get closed, locked, deleted or simply ignored without any response.
I hope responses to this issue will not be about how good a particular proprietary licensing is, since my argument does not aim to stand for free software, nor against it.
Instead, I am simply pointing out an error in the use of the word "copyleft", which I believe to be a significant error.

The error can be corrected quite easily by creating a new word for it and basing your success upon your own merit: it is a bit harder, but it does have the added benefit of being honest.

Best regards.

What's the current status of this dedicated repo, given that HL v3 has a copyleft module https://firstdonoharm.dev/build?modules=cl ?

I don't have an underlying question in mind, at this point, beyond understanding the EthicalSource landscape.