Being compatible for use with Legend of the Five Rings really has nothing to do with it, with all due respect. The intellectual property in the book (the fluff, in other words) would be designated as non-open content if there was any OGC in the book, which there isn't. WotC chose not to make it OGC, just as it hasn't made most of its books OGC. There are only two WotC books I know of with open game content: Monster Manual II (and only two monsters are OGC), and Unearthed Arcana, which is pretty much all OGC.
I don't know what, if anything, from OA has made it into the SRD, but I suspect nothing has, at least not yet.
EDIT: Looks like Eric beat me to the draw.