Led by Jaroslav Kysela, the project started from a Linux device driver for the Gravis Ultrasound sound card in 1998, and was developed separately from the Linux kernel until it was introduced in the 2.5 development series in 2002 (2.5.4-2.5.5). In the 2.6 version it replaced the previous system, Open Sound System (OSS), by default (although a backwards-compatibility layer does exist[/code]
This seems to confirm it. But the fact is, as I've just discovered, that slack 9.1 (kernel 2.4.22) either has it compiled in the kernel or has loadable modules for it. A contradiction?
EDIT: No contradiction if loadable modules.