[mimixco]

I can answer this. You do indeed have to offer the product "for sale," even if it's free. To get our trademark[0] for downloadable (free) software, we had to prove that we were advertising and offering the product for download and that someone did, indeed download it. Has to be across state lines, too!

For the apparel trademarks (hats, t-shirts) we had to show the proof that the clothing sales website was up to the public and prove with a transaction and photo of the finished clothing that we were, indeed, selling trademarked hats and shirts and producing finished goods. You even have to show clothing labels with your trademark on it or you won't get apparel marks for your software -- so no protection for your logo on swag.

Our hosted product is in a different trademark class because the USPTO considers downloaded software to be a product and hosted software to be a service. To prove use in commerce in the service class we had to offer the product (that one costs money, lol) for sale, prove a real transaction took place across state lines, and prove that the customer had taken delivery (welcome email, etc.)

It's quite a process but, as our trademark attorney (we used Tradmarkia) said, if you don't do all this your mark with either be denied by the USPTO, accepted and then challenged later by them, or contested by another applicant.

[0] https://trademark.trademarkia.com/m-88979084.html