The website says Bigger Reactors is licensed under LGPL 2.1.

I recommend adding a license file to the repo.

One way to do this would be to copy lgpl-2.1.md to LICENSE.md.

See also: Licensing a repository

BiggerSeries/Phosphophyllite#21

it exists, its just not at the repo root, this becomes jar root at build
https://github.com/BiggerSeries/BiggerReactors/blob/master/src/main/resources/LICENSE.txt