If you downloaded the file via github's web interface, make sure you got the "raw" file, and not an HTML wrapper. The file itself should be 3144 bytes.
After that:
git clone https://github.com/moneromooo-monero/monero-wallet-generator.git
cd monero-wallet-generator/
git show --show-signature
You should see "Good signature from..." with my key (4D6CEFC3). You will get a warning that the key isn't trusted, and that's expected, since you did not tell your gpg to trust my key.
Since the file ended up hosted on saddam's server, I will GPG sign the file itself as well for next version, so people don't have to use git for this.
Thanks, that worked! I didn't have the RAW file after all.