New works of art usually enter the public domain through a process involving death and patience. It is a rarer occasion that living people set about to make a resource public domain, and even rarer so when that effort involves thousands of people collaborating and pooling their time, energy, and money. That's what's happening on MuseScore.com with the first public review of the Open Well-Tempered Clavier score, a new edition of J.S. Bach's musical masterpiece (BWV 846-869).
That's why the Open Well-Tempered Clavier project (campaign on Kickstarter) was created: to make a modern, digital version of Bach's work, and to license it freely (in this case with the Creative Commons Zero—CC0—license remover). So that there is no doubt about allowed use—all uses are allowed and encouraged. The companion recording of the work, played on piano by Kimiko Ishizaka, also CC0, will be released in March of this year.
Participants in the public review of the score are asked to study the notation carefully, either in the browser or by downloading the individual scores into the open source MuseScore program. Compare the notes and markings to other editions of the score, or to the very manuscripts themselves, and note the differences. The MuseScore.com website has a feature that provides for the annotation of the scores (one of the advantages gained by making digital versions that are expressable in standard formats such as MusicXML).