nomacs is a free image viewer licensed under the GNU Public License v3. It is small, fast and able to handle the most common image formats. Additionally it is possible to synchronize multiple viewers. A synchronization of viewers running on the same computer or via LAN is possible. It allows to compare images and spot the differences (e.g. schemes of architects to show the progress).
Post By: Nikom Puket
License: Open Source
Developer: Markus Diem, Stefan Fiel and Florian Kleber