No. From their Engineering page: > ...our plan all along has been to make our entire code base open source; however, as anyone who has worked with such issues

No. From their Engineering page: > ...our plan all along has been to make our entire code base open source; however, as anyone who has worked with such issues knows, it is often not quite that simple. We are committed and will continue to work toward an open source environment. They have some open source bits (see https://spideroak.com/code https://spideroak.com/code) and presumably it's built on top of FOSS libraries, but still definitely proprietary.