Go to the store page and click on the flag just below the supported languages list on the left (marked red on mine).
And here's how I reported it in case you'd like to riff on that.
Here's my report text: "Selling an open source game in violations of its licenses (MIT, LGPL 2.1, LGPL 2, available at https://github.com/0ad/0ad) and without the permission or knowledge of its development team."
@gamingonlinux Love the Deck, new to Mastodon.