Hi @anyx, highly respect your project, but personally disagree with this notion/philosophy.
In my opinion, close-sourcing code is not the correct solution to a problem of malicious use. Firstly, it doesn't actually work: eventually malicious code will be written and open-sourced. Secondly, the system needs to be exposed to malicious code in order to develop strategies for counteracting it.
There may be other motivations, such as economic and anti-competitive ones, to close-source your code. If that's the case, I recommend you state them up front to preserve integrity.