PS_View is a PostScript and PDF previewer. It is multiplatform (Windows, Linux and Mac OS X), GUI program based on the Ghostscript engine. Key features include huge magnification, fast viewing of large documents, exact measuring, and restart.
Emma (Extensible Multi Media Architecture) is an open-source, modular, extensible, dynamic framework for declarative authoring and display of 2D and 3D interactive multimedia. It uses Lua for scripting and Ogre3D for rendering. http://www.emma3d.org
Doris is a Lua script driven OpenGL viewer with GUI widget extensions. Lua is a fast, powerful, portable scripting language. Lua bindings are provided to OpenGL, GLUT, GLUI (a GL widget library) and Luasocket (networking).