my general rule is that it's definitely OSR if it's compatible with every edition of D&D. So anything that does that is definitely allowed.
But it's not like anyone's saying that the Black Hack isn't OSR, and I'd accept submissions for Black Hack content.
While trying to figure out what BrightHammer was, so that I could answer this question, I found out that the person who wrote BrightHammer has me pre-emptively blocked on Twitter, so I'm not gonna accept submissions on that.
Basically, if it's not generically compatible with a bunch of stuff, I guess directly ask me and I'll look it up. I'm generally going to err on the side of yes, though, on the basic assumption that a) you and everyone else is acting in basically good faith and b) not that much hinges on me getting the exact definition of "OSR" wrong.