OpenBSD/sparc 2.1 is brought to you by the same people who did the first
free BSD sparc port (based on Chris Torek's 4.4BSD work).  Many more sparc
models and devices are now supported.

In addition to the providing SunOS 4.1 compatibility, OpenBSD 2.1 will
also run some number of SunOS 5 (SVR4) executables in binary emulation mode.

OpenBSD/sparc has gone though several development cycles since it's origin,
but the OpenBSD/sparc 2.1 release should be considered as "under active
development" rather than a production ready release.  There are still known
problems with the kernel and missing support for some common devices.

What this means is that if you try to install OpenBSD/sparc as a replacement
for SunOS or Solaris in a production envionnment, you will get the features
mentioned above, but probably not a stable/reliable system.  On the other
hand, if you're looking for an operating system for a personal workstation
or for working with unix tools and internals, you might find OpenBSD/sparc
quite satisfactory as released.