L5R too, IIRC. I've seen the same mechanic (albeit with different die sizes) used in indie stuff since, and I doubt AEG originated it in the first place. Like you said, a game mechanic can't be copyrighted, just the specific terminology used to describe an example of it.Was that the 7th Sea game system?
WotC probably could have bought Hasbro (and anyone else they wanted) if they'd managed to copyright Magic's tapping mechanics and gotten royalties from most of the CCG boom back in the day. "Turn a card, pay us our cut."
I think what @kenada is pointing out is that copyright is far from the only IP potentially at issue. There are patents, design patents, trade dress, etc. that can be at issue when discussing something like a game. IMHO this kind of thing is unlikely to be a problem, but I am no more a lawyer than anyone else here. A lot of these things have also probably lapsed for older games, assuming they were ever asserted at all.You can't copywrite mechanics, only their presentation, as Morrus said above. There are a lot of cookbooks that take advantage of this ....
"Explode" certainly isn't copyrighted. It is common parlance for "if you roll the highest value on the die, you keep rolling."Not to mention the term 'explode' when you roll a '0' on the d10.