GreenLight v2 has the same system requirements as a fresh Laravel 5.7 instance has, however it is expected that v2 would follow further versions of Laravel regarding compatibility as well.
These requirements (as of Laravel 5.7) are:
The rest of the required dependencies are defined in the composer.json file of the package.
This package is tested with previous Laravel versions as well, however it is always recommended to use the latest possible version of Laravel available.