PS doesn't have restrictions on what you can do with your content (like any decent program), so it's safe to use.
Though there are some pieces of software (most notably some cloud software) that try to restrict what you can do with your own content. Luckily this trend isn't very successful so far, so you're fine with most programs.
From an ethical PoV, I always prefer open-source software when it's available. But ethics are quite personal, so I won't dictate what you need to use. (if everyone on the programming team had the same ethics as I did, we wouldn't even be able to release the game for Windows and Mac, since nobody would be able to compile or test it there).