Is the question regarding intellectual property? Like how Disney guards its various franchises and brands (eg Mickey Mouse)?
We kind of already know what happens in that scenario, but historically – and even Disney has benefitted from this – anything which was part of the unwritten body of mythos was fair-game to use or remix. Modern copyright and trademark laws only affect that which was reduced to a fixed medium, like film or novels. And even then, the standard of originality – in the USA anyway – means that just recording a word-of-mouth story does not imbue a claim to the story itself, but merely its rendition on paper.
As a practical matter, so long as people still talk in-person and share their accounts and experiences, the rich human tradition of storytelling will not end, copyright be darned. If some new legal mechanism is invented to enforce “speaking crimes”, then we’re already zero steps away from an Orwellian nightmare where “thoughtcrime” is prohibited.
https://www.mozilla.org/en-US/about/legal/terms/firefox/
Thus, the answer turns in whether any Firefox binaries are used or distributed with LibreWolf. On the LibreWolf website, I don’t even see any binaries for LibreWolf that they host, except the Windows binary. For all other OS, they refer to that OS’s package manager. But even still, there is nothing to suggest that any Mozilla-compiled binaries are in LibreWolf, which only has source code commonality with Mozilla Firefox.
The answer appears to be: no.