He may do that, but users will use the free version. Since it is free software, many user-friendly changes are possible that tend to conflict with commercial i

He may do that, but users will use the free version. Since it is free software, many user-friendly changes are possible that tend to conflict with commercial interests. (Indeed, someone already made a post about the author's privacy policy changes, making the commercial software less valuable with zero lines of code.) While the author may make a few bucks, that kind of thing will not pass any due diligence, so his success may be quite limited.