Depends what nation you are in and how you obtained it.

Anyone can release software under any licence. As long as they are not breaking the licence they release under. Or the licence they use any 3rd party code is under

I do not think GPL has any rules about claims. Just actual actions. But if they released in under another licence. Then it is possible. (But unlikely). The licence has such rules.

So in most cases. Actual actions or lack of rather then claims. Based on the licence is your only option. And that would mean contact he authors of any included code. Or FSF etc.

Some nations have advertising rules. Depending on how and where it was obtained you may be able to contact their advertising standards association equiv.

But providng for free can often weaken this. Although it is likely far from an absolute excuse to false advertising.