RT-Thread RTOS is a real-time operating system for 16-bit to 32-bit microcontrollers, with components which include a hard real-time kernel, a command line shell, a device virtual file system, and a graphic user interface. RT-Thread/GUI is a graphic user interface integrated with RT-Thread. It provides a multi-window, multi-thread graphic user interface. Rich widgets are implemented in RT-Thread/GUI, such as label, button, checkbox, textbox, etc. The typical RAM usage of RT-Thread/GUI is less than 20kB RAM.
If you pay attention to this open source RTOS, you can wait for 0.4.x series release in next month, which will include AVR32, MIPS branches.
The 0.4.x series development activities are placed on Google Code.