YAAC is licensed as open-source software under version 3 or later of the GNU Lesser General Public License (LGPL), and source code is available under the terms of that license.
Note that some of the third-party components used by YAAC have other licenses. For example, the RXTX library is licensed under the LGPL with a special qualifier for linking to other-licensed software. The Apache Commons libraries are licensed under the Apache license and source code is available on the Apache website at http://commons.apache.org/components.html. The OpenMap™ library (created by BBN) is licensed under a custom open-source license that is not compatible with the GPL (but is compatible with the LGPL); per the terms of that license, the OpenMap™ source code may be downloaded from http://openmap-java.org/. YAAC is presently using OpenMap™ Version 5.0.
The OpenStreetMap data is licensed under either the Creative Commons CC-BY-SA license or the Open Data Commons Open Database License (ODbL). The Shuttle Radar Topographic Mission (SRTM) elevation data has been placed in the public domain by the U.S. Geological Survey. The weather radar maps and reporting region shapefiles have been placed in the public domain by the U.S. National Weather Service.