In Smalltalk-80 they're on the left side, see e.g. https://github.com/rochus-keller/Smalltalk

I recall reading that the reason is that the mouse pointer is more likely to already be near the left of the window, because more of the text is on the left, especially in a programming language.

GnuStep uses WindowMaker, which shows scroll bars on bottom and left because that’s where they were on nextstep.

It actually doesn’t use WindowMaker. GNUstep is a reimplementation of core Apple frameworks, and can run in any DE (including Windows)

WindowMaker is its own thing that just so happens to be trying to recreate software from the same ecosystem as GNUstep, but they don’t depend on each other.

Combining them tho does give you that genuine experience

Note that Window Maker is a completely separate project with its own GUI toolkits (WINGs - it literally means "WINGs Is Not GNUstep" :-P).

That's where they were on NeXTStep:

http://toastytech.com/guis/ns332.html

And it's actually a pretty good place. Just like the whole "a menu is just a window with a list of buttons" idea was great.

If we lose that website, we will lose so much computer history and knowledge.

.. serveral 'ours layter ...

Thanks for that rabbit hole of nostalgia, just remembered how wild Mac OSX 10.1 in its first release was. It was a real game changer, and looked great (albeit a bit slow on my poor G4 Cube).

As others mentioned, this is due to the NextStep theme which is the default. However GNUstep supports other themes and can have the scrollbars at the right position too.