The source is GPL-3.0
DayBoard's source code is licensed under the GNU General Public License, version 3, with no later-version option. You can read it, change it, and build it yourself from the GitHub repository, as long as you share your changes under the same license.
The official build
The signed official DayBoard build is free to download. Its AI features need DayBoard Pro, a one-time $5 purchase (launch price) that funds ongoing work; during the beta, they're free too. See pricing. Buying Pro doesn't change your rights under the GPL, and AI provider usage is never part of the purchase.
Third-party components
DayBoard's dependencies keep their own licenses, listed in the app under Help → Open Source Licenses…. This site uses the Fraunces and Hanken Grotesk typefaces under the SIL Open Font License (Fraunces, Hanken Grotesk).
Trademarks
Google Calendar, Google Tasks and Gmail are trademarks of Google LLC. Apple Reminders and macOS are trademarks of Apple Inc. DayBoard isn't affiliated with or endorsed by Google or Apple.