I don't understand either. The Promise driver (I think this is carmel?)
found at
http://www.promise.com/support/download/download2_eng.asp?productID=125&category=all&os=100#
seems to be GPL. I haven't tested it extensively yet, but it appears to
provide scsi device nodes that grub recognizes readily.
Why are there two GPL driver projects for this card, and what is the
difference? Is there something wrong with promise's driver, or
inherently superior in the kernel driver? How is one supposed to
choose? There is very little documentation for either driver, so it is
quite unclear which is appropriate for a given application.