What is the difference between MuseScore.org and MuseScore.com?
MuseScore.org is home to the open source MuseScore program for Windows, macOS, Linux, and its developers, contributors and users community. Its forum is the ideal place to ask any question related to the MuseScore program.
MuseScore.com is a community site to share your sheet music with your friends via the web and for the mobile apps for iOS and Android. The site has social features such as embedding, commenting, annotating, statistics, groups. The site offers free accounts, but has a Pro Account for those who want more.
See also How and where to ask for support