Mod Creators are permitted to use all ARK Survival Evolved assets within their ARK Survival Ascended Mods. With two important exceptions:
1)  Mod Authors may not reupload Official DLC maps as mods.
2) Content and Assets that were added specifically for  the Aquatica DLC are not permitted for use.

Mod authors are welcome to import assets from the ASE DevKit and we encourage it if it makes your development efforts easier.

Animation BPS do not support using montages in the animation graph. in ASE this was possible. if you import any Custom animation blueprints that had montages in the animation graph it will crash.

It's official from the corporate top-boss: creators can use all ATLAS assets within ASA mods as they see fit! 

Only for use within ASA mods, of course.

Gameplay Content & Features exclusive to official paid DLC content may be used by mods, but enforcing ownership of the DLC is required if any of the official gameplay art assets are used (Models, textures, animations, etc).
If a mod uses these features but uses all of their own visual assets then enforcing DLC ownership is not required.
Making a child or copy of the existing content and simply removing any DLC ownership enforcement is not permitted, the art assets must be replaced if doing so.

Map Assets from official paid DLC maps (Lost Colony) are available for mod map authors to use, but unless you are copying the assets into your mod files the cloud cooking system will automatically flag the mod as requiring the paid DLC (Lost Colony), if you are copying the specific map asset into your mod files itself, no additional ownership check is necessary.

Premium Map note:
Premium maps are not permitted to have dependencies on official paid DLC.
Premium maps that want to use Lost Colony map assets (or from any future paid DLC) must copy them into the mod so as not to trigger the dependency, otherwise they will be rejected from release.