CopperSpice is a set of individual libraries which can be used to develop
cross platform software applications in C++. It is a totally open source
project released under the LGPL V2.1 license and was initially derived
from the Qt framework. Over the last several years CopperSpice has
completely diverged, with a goal of providing a first class GUI library
to unite the C++ community.

Our motivation for developing CopperSpice was to change the fundamental
design and turn the existing framework into a set of libraries for C++
developers. We are accomplishing this by leveraging modern C++
functionality, new technology, and modern tooling. CopperSpice currently
requires C++17 or newer.

WWW: https://www.copperspice.com/