Pencil2D is a free and open-source 2D animation software available for Windows, Mac OS, and Linux. It is a fork of Pencil. The application uses a bitmap/vector drawing interface to produce simple 2D graphics as well as animation. Pencil is written in C++ and is Qt-based. The application license is GNU General Public License.
It started as a simple "pencil test" program by Patrick Corrieri, extended to the current Pencil application mainly by Pascal Naidon. It was forked as Pencil2D by Matt Chang and is being actively developed.