Essentially, it seems like all we want is to list in the wiki a small list of BIOS interrupts that are useful to bootloader development (real mode OS' are a dying specie nowadays). I'm no legal expert, but I'm pretty sure that M. Ralph Brown has not become the owner of the "which numbers to put in which registers in order to do which things". To my poor legal knowledge, all he owns is "the text he has written", I don't think there is any legal owner of the information condensed in this text.
As an alternative, M. Brown had to get that information from somewhere, and we could very well find the same information from other sources. I first thought of Wikipedia, which has some information on some very common interrupts, although very generic, but is Creative-Commons-licensed.
To find more, I had a fun time playing the n00b guy and typing very simple questions (like "How to read sectors using BIOS") on Google. Apart from a few BIOS modding tutorials (yes, I'd never thought of doing that), I found two potential sources that id NOT Ralph Brown's:
At the very least, maybe we could get a list of common interrupts from famous BIOS manufacturers like Phoenix, although I somehow doubt it.