Can I turn off the trial and use only free features?

Yes. Open Settings > Application > Advanced Settings & Privacy… and turn off Licensing & Pro Features, if that switch is shown. BetterDisplay then permits only free features.

This disables the app’s licensing functionality, including purchasing, activation and access to trial or licensed Pro features. It is not merely a way to hide a trial notice while keeping Pro features active. Check that your display setup does not depend on Pro features before changing it.

Turn the switch back on if you want to use licensing and Pro features again. Turning licensing off does not pause or restart the trial. The app does not offer a trial-reset feature. See trial expiration and licensing permission.

Using free features remains subject to the app’s license terms, including the separate requirements for business use.