Wow, such negativity..
They still have the OSS compatibility layer.. as for the official OSS4, that isn't ported to OpenBSD, and it shouldn't be either.
What this allows for is a base ability to "multiplex" audio sources, i.e: instead of one program hogging the audio(4) device.. they can send data to a unix socket handled by aucat(1).
Basically it's a base replacement for things like esd or aRts.. all of which use the OSS API themselves.. a sound proxy if you will..
That is all.