Terrain Toolkit Re:

The present version of the Unity Terrain Toolkit is based on :
The Unity Terrain Toolkit from the Unity Summer of Code 2009 All code by Sándor Moldán, except where noted. Contains an implementation of Perlin noise by Daniel Greenheck. Contains an implementation of the Diamond-Square algorithm by Jim George.
The present version of the Terrain Toolkit is an adaptation and enhancement of the original tool (V1.0.2) for the newer versions of Unity. Beyond the necessary code adaptation, a cosmetic refactoring was performed (GUI mainly but also core code). This being said, the whole toolkit works as the original toolkit was designed.
The original package (Unity 4 compatible) is bundled in the 'original' folder. It comes with its associated documentation.
NOTICE : Terrain Toolkit Re: is the continuation of the discontinued Terrain Toolkit 2017 : the toolkit will now stick to the newest Unity LTS version available.
The original toolkit was FREE, this version too !
Enjoy and keep it a popular tool !