YAAC ("Yet Another APRS Client") is a (mostly) platform-independent Java application written by Andrew Pavlin, KA2DDO, for monitoring and contributing to the Automatic Packet Reporting System (APRS) network (invented and trademarked by Bob Bruninga, WB4APR).
YAAC is Free Software; it is an Open-Source program, licensed under the GNU Lesser General Public License, and complete source code is provided (including references to the source code of third-party libraries used in YAAC). Feel free to create improvements and extensions to YAAC.
YAAC can be used as a stand-alone APRS client, an APRS RF-Internet gateway (I-Gate), or as a AX.25 router. It supports at least 15 different data reporting views as delivered, and can be extended with user-written "plugins" to add more functionality. YAAC's map rendering does not depend on Internet connectivity, so it can be used wherever a portable computer and radio/TNC can be located.