Lets take this case: Neo4j is a open-source graph database with commercial features/support. They recently developed a lot of new official drivers ( about time! ). The .NET one in particular used the 4.6 framework, some community members forked it and wanted to collaborate on adding support for .NET's new 'open-source' ( LOL ) core framework.
A awesome community member added supported for that, he posted the fork and was gathering feedback when one of the maintainers said: "You may personally be happy not to expect official support but if we host such code or make any such releases, someone somewhere will expect it to be supported.". If thats your attitude why EVEN POST THE PROJECT ON GITHUB?
Case in point: https://github.com/neo4j/neo4j-dotnet-driver/issues/52#issuecomment-221667996