Sympiano is free to use. You may install and use it on your own machines for any purpose, personal or commercial, including in music you release or sell. You do not owe anything for it.
Please do not resell Sympiano itself, repackage it as your own product, or redistribute modified copies. If you want to share it, link people to www.sympiano.com so they get the signed installer and any updates.
Sympiano is provided as is, without warranty of any kind. To the maximum extent permitted by law, the author is not liable for any damages arising from its use. If any part of this notice is unenforceable in your jurisdiction, the rest still applies.