Something occured to me (and a collective uh-oh arises from the crowd ;). Whenever I write specs (now-a-days, anyway), I use License. I went back to look at the old mdk-rpm howto for a proper group and noticed that chm*uel's skeleton.spec uses Copyright.
It seems almost all official mdk rpms are using License. Is it safe to go with that and assume that's fine for all rpm or hybrid rpm based distros?
