Sector/Sphere is open source software under the Apache 2.0 license. The software is written in C++. The server side supports Linux only. The client side supports Linux and Windows, with OSX being ported to.
Sector/Sphere is available for download from the Sector SourceForge project web site. The release package contains source code, Sector/Sphere API, programming examples, Sector file system access tools, and detailed documentation.