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.
There is still the last AGPL version. The most effective retaliation is to make a fork that is much, much better than the closed version. Less drama, more work, I know.
1. Clone the repository. Make an insignificant change to the initial commit in order to change all commit hashes. Push to github as a new repository.
2. Create a password "protected" zip file (or smaller volumes) containing the repository. Use a password that's easily found in common wordlists. Commit it to another project and push to github.
Microsoft GitHub may be centralized, but it's not omniscient. RIAA may be a control freak, but it's not omnipotent. Let information be free for all.
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.