What operating systems does Subversion run on?

All modern flavors of Unix, as well as Win32, BeOS, OS/2, and MacOSX.

Subversion is written in ANSI C and uses APR, the Apache Portable Runtime library, as a portability layer. The Subversion client will run anywhere APR runs, which is most places. The Subversion server (i.e., the repository side) is the same, except that it will not host a Berkeley DB repository on Win9x platforms (Win95/Win98/WinME), because Berkeley DB has shared-memory segment problems on Win9x. FSFS repositories (introduced in version 1.1) do not have this restriction; however, due to a limitation in Win9x's file-locking support, they also don't work in Win9x.

To reiterate, the Subversion client can be run on any platform where APR runs. The Subversion server can also be run on any platform where APR runs, but cannot host a repository on Win95/Win98/WinMe.