BRL-CAD is a powerful cross-platform constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing for rendering & geometric analyses, network distributed framebuffer support, image & signal-processing tools.
NEW: Version 1.10.0 is out - Apple Silicon is now natively supported.
dcpTool is a tool for editing DNG camera profiles (DCP files). dcpTool can convert DCP files to and from binary form to an editable XML form, and can also directly do a number of useful transformations to DCP files such as "untwisting" them.