WideStudio is an Integrated Development Environment (IDE) for building window applications in C++, Ruby, Python an Perl for Windows, MacOSX, Linux, FreeBSD, SOLARIS and other unix and BTRON and T-Engine. This is open and free (under MIT/X Consortiun Lice
banshee-- A toolkit for building constraint-based program analyses
Griff is a collection of projects including: (i) Sarl3 - Sets and Relations Library for doing Formal Concept Analysis (FCA); (ii) RJL a progamming language combining both static and dynamic typing, and (iv) PIG a simplistic triple store.
VSGE is a platform-independent, "very simple" game engine based on the SDL and OpenGL libraries. Using unorthodox technologies when appropriate, it strives to make developing non-trivial games simple and fun.