U++ : A C++ cross-platform rapid application development suite focused on programmers' productivity without sacrificing runtime performance

U++ is a C++ cross-platform rapid application development suite focused on programmers' productivity without sacrificing runtime performance. Based on strictly deterministic design, it provides a viable alternative to garbage-collected platforms, even for business logic oriented problems.

• Licenses : BSD Revised, LGPL, GPLv2, Public Domain, zlib/libpng
• Operating Systems : POSIX, Linux, Windows, FreeBSD
• Implementation : C++

Open Tool Kit (Otk) : A portable widget library for making graphical user interfaces for C programs

Open Tool Kit (Otk) is a portable widget library for making graphical user interfaces for C programs. It emphasizes simplicity for the application programmer without eliminating capability. Based on OpenGL, Otk supports Linux, Unix, and other OSs neutrally and efficiently. It is simple and compact, and it strives for easy compilation and linking to other applications. In seeking to address several issues associated with earlier graphics APIs, Otk explores some interesting methods, such as window-relative layout instead of pixel-based layout.

• Licenses : LGPLv2.1
• Operating Systems : Mac OS X, Windows, POSIX, Linux
• Implementation : C