Is editing Admin plugin permited? First files to change?

I would like to know if it is possible (in terms of licence) to create a new plugin based on Admin Plugin?
My intention is to use only (and expand) the statistics part. I would like to create a plugin that consumes information from an external service and shows charts with statistics.

If this is possible, which are the first files to modify in order to have a route pointing to localhost/mygravpage/copyOfAdminPlugin ?

Thanks in advance,

As you can see in, Admin (as Grav itself) is MIT licensed.

There is a way to add dashboard widgets without editing Admin which is hooking into onAdminDashboard from your own plugin, see