Very exciting to see the draft license! I have a couple of immediate questions based on a first read-through.
It's not clear to me what would constitute a replacement of the official core rules as opposed to an addition. Say I was writing a module that was focused on a particular kin such as Halflings or Wolfkin and I wanted to introduce a rule that anyone playing a Halfing take +2 AGL and -2 STR, or that anyone playing a Wolfkin take +2 STR and -2 CHA at character creation. Would this count as an additional rule, or as a partial replacement of the rules on how to calculate Attributes? Would it make a difference if such a rule was explicitly optional?
How attributes are genereated is a core rule and changing it would thus not permissable under the license. The reason behind this is that we want all third-party publications for the game under this license to be compatible with each other and with the core game.
You could, however, add new innate abilities, heroic abilities, professions, secondary skills, magic schools, spells etc unique to Halflings or Wolfkin.
It's not clear from Section 2 whether the core rules can be quoted in a module. It says that terminology, names of creatures, and locations can be used and that you can't include a complete copy of the core rules. But there's a lot of space in between. Can the core rules be quoted in part? This is most likely to be relevant in, for example, an adventure module that includes monsters from the core rulebook and monsters the writer of the module has created. Having stats and attack tables for some of the monsters in the module itself but having to refer back to the core rulebook for others is not very user-friendly and so writers will likely want to include the information for all monsters and NPCs in their adventure within the module itself for ease of reference. It's not clear whether or not the license permits this.
If using monsters from the core game in your adventure, we would recommend that you simply refer to a page in the core rules rather than copy the text.