It‘s profoundly weird that we are even having this debate. No one gets up in arms about not being use the Monopoly Open License.....
A monopoly open license isn't needed. Here is a forum full of Monopil-ish games: Inspired By Monopoly - Variants and Rip-Offs
Want something more current? Go look at Words with Friends; it is scrabble with a different name.
Rules can't be copyrighted. What they release under CC shouldn't require any license.
Game companies in the 80s knew this so they trademarked everything as a way to create a legal blocker, to the point It is was integrated into templates resulting in Nazi(tm) in the Marvel RPG.
Many of the things they are hiding behind the SRD (like elf, orc, dwarf, power attack, fey touched, fireball, goblins, dragons, poison traps etc) don't need licenses as they can't be copyrighted.
Unique creations (kender, mind flayer, probably owlbear), could be trademark violations and/or be very difficult to redescribe without getting close to a copyright violation. This was the only real value of the SRD: it meant you didn't have to go through the monster manuals etc with a fine tooth comb to grind off the names/descriptions for unique creations.
However, if you had the time, you could take the statblock of every single creature in the monster manual, change the name & rewrite the description from scratch and be legal.
I am a data nerd so I would use a generic format of CR-terrain-alignment-type-bodystyle-size. Like 0.25-forest-neutral-beast-quadruped-small-01 (or 0.25FNBQS01 for short) and then have a list of creatures that could be (war dog, wolf, immature dire wolf, sabretooth bobcat, young lion, etc). I would like to do the reverse as well and have a section on dire wolves that lists which creature types can be for pups, immature, adult, pack leaders.