"In practice it is intractably hard to make any significant modification to a binary, and even if you could, you would then not be legally allowed to e.g. redistribute."
It depends on the binary and the license the binary is released under. If the binary is released to the public domain, for example, you are free to make whatever modifications you wish. And there are plenty of licenses like this, that allow closed source software to be used as the user wishes. That doesn't make it open source.
Likewise, there are plenty of closed source projects who's binaries we can poke and prod with much higher understanding of what our changes are actually doing than we're able to get when we poke and prod LLMs. If you want to make a Pokemon Red/Blue or Minecraft mod you have a lot of tools at your disposal.
A project that only exists as a binary which the copyright holder has relinquished rights to, or has released under some similar permissive closed source license, but people have poked around enough to figure out how to modify certain parts of the binary with some degree of predictability is a more apt analogy. Especially if the original author has lost the source code, as there is no source code the speak of when discussing these models.
I would not call that binary "open source", because the source would, in fact, not be open.
It depends on the binary and the license the binary is released under. If the binary is released to the public domain, for example, you are free to make whatever modifications you wish. And there are plenty of licenses like this, that allow closed source software to be used as the user wishes. That doesn't make it open source.
Likewise, there are plenty of closed source projects who's binaries we can poke and prod with much higher understanding of what our changes are actually doing than we're able to get when we poke and prod LLMs. If you want to make a Pokemon Red/Blue or Minecraft mod you have a lot of tools at your disposal.
A project that only exists as a binary which the copyright holder has relinquished rights to, or has released under some similar permissive closed source license, but people have poked around enough to figure out how to modify certain parts of the binary with some degree of predictability is a more apt analogy. Especially if the original author has lost the source code, as there is no source code the speak of when discussing these models.
I would not call that binary "open source", because the source would, in fact, not be open.