Removing software from a repository does not prohibit users from installing it. It just asures the user that their system is free from user subjugating software. If someone wants to write a game and is capable of writting it for that engine, they are prabably capable of installing the game engine from outside repositories.
When there is free software for a game engine, I do not see a reason to remove it. Otherwise, if its exclusive use is to run nonfree software, in practice it does not provide freedom to the user.
