FLOSS, Free Software Foundation
FLOSS (or FOSS) is set up to support free software downloads and also the option to re-write the code in a software program to the persons preferences and then to share this new improved version of the software on for free to others where they can do the same. The term coined for this is called "copyleft".
Here are some examples of FLOSS:
http://www.gimp.org/ - a popular freely distributed piece of software for such tasks as photo
retouching, image composition and image authoring, powered by a great
bunch of script and plug-ins.
http://www.skencil.org/ - a Free Software interactive vector drawing application. Known to run on
GNU/Linux and other UNIX-compatible systems, it is a flexible and
powerful tool for illustrations, diagrams and other purposes.
http://podofo.sourceforge.net/ - a library to parse and create PDF files, includes a PoDoFo browser useful to "debug" PDF files.
http://www.graphicsmagick.org/ - GraphicsMagick is the swiss army knife of image processing. It provides a
robust collection of tools and libraries which support reading,
writing, and manipulating an image in over 88 major formats including
important formats like DPX, GIF, JPEG, JPEG-2000, PNG, PDF, SVG, and
TIFF.