[squintychino]

Why do you have to redistribute something in order to modify it? Just modify it for your own personal use.

[delinka]

Since when do you need a license to modify something for your own personal use? If they've given me access to the source, I can just start editing to my heart's content...

[chimeracoder]

Practically, yes, but legally, you may not have the rights to.

That's why it's explicitly listed as part of Freedom 1 of the four freedoms of software: https://www.gnu.org/philosophy/free-sw.html

[ballard]

DVD players.

[tensenki]

I can't think of a single use case where I would want to hack on a 32 year old OS without distributing it.

[Someone]

Not quite the same, but it may be good enough for you: I guess you can distribute a patch, combined with a URL to the original download.