It seems that app mods, such as for games, are generally considered to be derivative works and thus illegal. Chrome extensions, though, don't have the same reputation, even for the well-known extensions that modify all sites by default. Is this modified user experience on copyrighted sites not a derivative work? Vimium, for example, modifies the navigation experience and is enabled for all by sites by default. Grammarly, as another example, modifies text fields when a user is typing into them. Grammarly also makes a lot of money, which it seems like would open it up further to litigation.
How is it that distributing a mod of a copyrighted desktop app seems to be generally illegal, whereas distributing a Chrome extension that modifies copyrighted sites is not generally discussed as illegal?
