International Music Score Library Project

The International Music Score Library Project (IMSLP), also known as the Petrucci Music Library after publisher Ottaviano Petrucci, is a project for the creation of a virtual library of public domain music scores, based on wikis.
Current operation.
IMSLP states on its site
that it is owned by Project Petrucci LLC. Physical contact information is provided, listing only an address in the United States.