Fast: Papaya is designed for efficiency. It starts up quickly, and is already significantly faster than other popular editors at zooming, panning and brushing.
Open: Papaya is completely free. The entire source code is open and is MIT-licensed, which means anyone is free to use and extend the code, even for commercial purposes.
Beautiful: While most other open editors use bulky UI toolkits, Papaya is rendered entirely on the GPU, with pixel-perfect precision and complete control over the visual design. I'm designing Papaya to be as beautiful as the images it will help create.
Cross-platform: Papaya runs natively on Windows, Linux and OS X.
EasyTab is a single-header multi-platform drawing tablet library that was released as an offshoot of Papaya.
Papaya is a work in progress, and could really benefit from your contributions.