
Danger from the Deep (known as dangerdeep or DftD) is a free (as in free speech), Open Source World War II german submarine simulator. The program and source code is available under the GPL license and most of the artwork/data is released under a Creative Commons license (Attribution/NonCommercial/Non-Derivative works).
DftD is currently being developed on Linux (i386 and AMD64) and Windows. There are binarys available for Linux (i386 and amd64), Windows (32bit) and there are some old packages for MacOSX. Danger from the Deep makes use of SDL/OpenGL and thus should be portable to other operating systems or platforms.
This game is planned as tactical simulation. It’s current state is ALPHA, but it is playable.
SkyChart III is a planetarium and telescope control program that shows the sky from any location, past or future, on Earth or beyond.