Balsamiq Wireframes for Desktop can open both local BMPR files from your computer and Balsamiq Cloud projects.
For LOCAL FILES, there's a fully functional 30 day trial. Afterwards, you'll need to buy a license to edit your work. Viewing BMPR files remains free even after the trial ends.
Working on projects hosted on Balsamiq Cloud doesn't require any additional license on top of your organization's Cloud subscription or trial.