You don’t have permission to access the requested object. It is either read-protected or not readable by the server.
Environment: Win 8.1x64 with XAMPP
No, this is not something that can be fixed. The file is there for a reason (it’s the license, and will be picked up before any route), and the security is there to stop people linking directly to it. So really can’t be fixed. All i could do is change it to LICENSE.txt or something so it’s less likely to conflict.
How you change it is open to you. But IMHO it should be fixed, otherwise it is not possible to have sub-page called /license without patching you’re grav installation after an update…