That is a really good question. I had to think about it for a moment. I think I am looking at it a little from both sides, but mainly from the perspective of creators. If the goal is to allow others to creat content and feel safe, then I just don’t see the ORC as needed.
See here as an example: http://www.lotfp.com/RPG/3rd-party-support
If the thought (not yours but in general) is ORC will become hugely popular, and people will not be creating for WotC and that is good because fuck WotC, then meh.
I think most of the ORC hoopla is virtue signalling. For example, Monte Cook Games has virtue signaled their support of ORC. Meanwhile, their own ‘open’ license, not even a year old yet, is anything but open, complete with morality clause.
Good luck with your game, btw. Make sure you let us know when it drops. I’ll certainly pick up a copy.
And I would say in reply, that's actually a really good license framework for what I want to do. About the only thing I would add that I think has value to the layman user would be a more concrete expression of what is and isn't considered "fair use"... not that someone couldn't in theory use anything and claim fair use, but rather "these are absolutely things I won't come after you for and its spelled out clearly in the simple license specifically so you don't have to have any doubts."
For example, depending on the company you're making a compatible adventure someone might only feel safe listing the monsters in an encounter as "Five Orcs (HP 7, 5, 6, 6, 8 ), see DMG p. XXX" or that an NPC is a "CG Fighter 10" because that way you're using basically none of their content in expressing the encounter and it minimizes the risk of someone as lawsuit happy as They Sue Regularly.
By contrast, I'd want to clarify for those wanting to make compatible adventures; "all monster stat blocks found in the Player's and GM's Guides may be reproduced in full in your works" and "You may include the full statistics of any NPCs and pre-generated PCs created using the rules for Ruins & Realms in your work."
In the same vein... "If you create a new subspecies for a species that specifically allows you to build a wide array of subspecies (ex. Beastmen, Eldritch or Mutants) or create a new trap, hazard, affliction, vehicle, structure or magic item using the rules systems in Ruins & Realms, you may include the full text of the selected traits in your description of the subspecies or other item in your work." (to clarify... Beastmen is a catchall for a wide variety of beast/human hybrids created by biomancers in a prior age. The creation rules involve picking two or more traits from a list of options with several example species and which of the traits they have also being listed, but is far from exhaustive. If your work required a different type of beastman and wanted it to be available for players, I consider it fair use to write out the full text of each selected trait instead of just listing the traits, because the former is going to be more useful to potential players due to less need to cross-reference).
Similarly, I'd probably include something to the effect of "You may reference any of the racial and setting lore from the Player's and GM's Guides in your works provided you do not duplicate it in full nor make any changes to the depictions of existing named characters (ex. killing off a particular named NPC as part of your adventure or turning a character depicted heroically into a villain) or locations within the setting (ex. destroying a settlement in the default setting area). You may set your work elsewhere in the default setting that has not been depicted (its a huge world and the default setting only a small part of it) and what you do with your original characters and locations is for you to decide. If you decide your work requires major changes to the default setting's cosmology (ex. a benevolent demon, playable necromancers), please note in your product that your work does not take place in the default setting, but its own world."
It's not so much "these are the only things you can employ under fair use" as it is "the copyright holder unquestionably considers these elements to be fair use and thinks using things like full monster stat blocks will make your product look better (and thereby draw more positive attention to the system as a whole)."