gdat is built for Intel macOS and so requires Rosetta 2 to be installed.
You can install Rosetta 2 with:
softwareupdate --install-rosetta --agree-to-license
Note that it is very difficult to remove Rosetta 2 once it is installed.
Installing gdat means you have AGREED to the license at:
https://www.getgdat.com/home/download/terms-of-use