Horos™ is a free, open source medical image viewer. The goal of the Horos Project is to develop a fully functional, 64-bit medical image viewer for OS X. Horos is based upon OsiriX and other open source medical imaging libraries. Horos is made freely available under the GNU Lesser General Public License, Version 3 (LGPL-3.0). Horos is linked against the Grok JPEG 2000 library, for fast viewing of JPEG 2000 images. This library is licensed under the terms of the GNU Affero General Public License.