No other file that I could see in the repository of those that I checked had any license terms either.
In other words, as it stands this is not open source under any useful definition.
Which is sad because it looks very cool.
Ideally though, for the sake of people looking at the GitHub repo, I think they ought to do the following:
1. Rename LICENSE file to COPYRIGHT and change the line
License: MIT + file LICENSE
License: MIT + file COPYRIGHT
3. Optionally, delete the LICENSE.md file unless it is useful elsewhere.
Assuming of course that having the license text and not just copyright notice in LICENSE won’t interfere with R packaging tools once the DESCRIPTION file specifies to use file COPYRIGHT instead.
But to e.g. import a Minecraft world and render it with the rayshader package? That might actually be a fun idea!
I still need to add support to add voxels from R and retrieve them, but should be straightforward, the hard part was putting together the rendering engine.