After considering all your replies, I am proposing the following solution for the platform.
Blender Depot never mentioned that it will list free or paid add-ons. It clearly mentioned open-source add-ons in the video and on the site. But by doing this, paid add-ons which are open source (please keep in mind that open source does not mean free software) got listed on the site which ended up harming the developers of the add-ons which spent time in developing them (as even I develop and sell paid add-ons for Blender).
Going forward, the platform would be updated to redirect users to purchase page (if they sell through the Blender Market or Gumroad) rather than directly downloading from the site. Although I am not sure how this would be fair for people that don’t sell through these platforms.
Also, since Blender Depot is built on the GitHub search, it’s hard to implement these features directly in the platform. Hence, we would require a user submitted add-ons list in the future that this platform could use(possibly discuss more on this).
Either way, Blender Depot is supposed to be for the good of the Blender Community and I don’t aim to harm the developers of the add-ons through this platform.
What do you say to that? After all, when people simply steal ideas, just because of a stupid idea to make everything open, what is the motivation for development and progress? I am sure, if there were no such cases, everyone would be happy. And this is not the case about the black sheep in the herd, here we are talking about really tens of thousands of man-hours that are actually under threat.
This is a double-edged sword - without such openness, the number of additions would be much less, but that would not prevent the development of the programs themselves anyway.
p.s. Blender is more like an exception in terms of commercial success. And without the genius of the people who developed it, no system will give such an advantage.