VPaint is licensed under the MIT license.
This includes all files outside the 'src/Third/' folder, but also the Qt project files within the 'src/Third/' folder (files with a '.pro' extension).
The 'src/Third/' folder contains third-party libraries, shipped with the distribution, which VPaint depends on. These are covered by different licenses which you can find in the 'src/Third/' folder. All these licenses are compatible with the MIT license.
Eigen is primarily MPL2 licensed. See src/Third/COPYING.MPL2 and these links: http://www.mozilla.org/MPL/2.0/ http://www.mozilla.org/MPL/2.0/FAQ.html
GLEW is primarily BSD-style licensed. See individual source code files in src/Third/GLEW
VPaint also depends on Qt, even though it is not shipped with the distribution. Qt is primarily licensed under the LGPLv3. See src/Third/COPYING.LGPL3