It is not proof. It is a clear derived work infringing on the copyright of Nintendo.
Depends of the country, a lot of countries have exceptions for interoperability (at least the whole EU) and since these projects are mainly used to make ports to other systems, it may be covered.
alt Hacker News
Depends of the country, a lot of countries have exceptions for interoperability (at least the whole EU) and since these projects are mainly used to make ports to other systems, it may be covered.