The landmarks in the Previous Release list identifies that 2.2.1 was the 1st Windows fork.
But there’s not a similar note for macOS. (And the original flavor of Linux was not noted in the 1st release in 2001. Amended that RedHat 7.X Linux system was the initial OS! If that designation is wrong, please say so.)
The ticket says it required a then-new version fo gnome to work. I wonder if that was the first cross-platform support. BTW, OSX 10.4 was then state-of-the-art!