I found this on the About page on the official Pygame website:
Truly portable. Supports Linux (pygame comes with most main stream linux distributions), Windows (95, 98, ME, 2000, XP, Vista, 64-bit Windows, etc), Windows CE, BeOS, MacOS, Mac OS X, FreeBSD, NetBSD, OpenBSD, BSD/OS, Solaris, IRIX, and QNX. The code contains support for AmigaOS, Dreamcast, Atari, AIX, OSF/Tru64, RISC OS, SymbianOS and OS/2, but these are not officially supported. You can use it on hand held devices, game consoles and the One Laptop Per Child (OLPC) computer.
I suspect this page is severely outdated as it doesn't even mention Windows versions beyond Vista, but it's quite intriguing to me that Pygame could potentially run on such old platforms.
What exactly does "contains support, but not officially supported" mean? Does it mean they could they technically run Pygame, but aren't thoroughly tested for bugs? Or are they just listing systems they think could run it, if they were willing to code it in?