Legal usage policy
Install MuseScore only on machines you are allowed to administer. Respect school, employer, and venue software policies.
Scores you create remain your responsibility regarding copyright. Do not distribute someone else's copyrighted sheet music without permission, even if you engraved it in MuseScore.
GPL 2.0 (as listed on Uptodown for Windows) governs the program itself. Redistributing modified program code requires following GPL obligations. Your original compositions are separate works.