Your bookmarks are secure and private, all stored client-side. No one can access them besides you and other people who have access to your device physically.
Yes, Bookmarker is completely free.
They could not get compromised on our servers, as all of the data for your bookmarks are stored client-side on your device. The only way it could get compromised is if someone hacked your device, and that would not be related to us.
We are attempting to provide a easier way to bookmark your pages, through a website. This will be forever free, as long as we operate it.