Pencil is an open-source GUI prototyping tool that's available for ALL platforms. Pencil is built for the purpose of providing a free and open-source GUI prototyping tool. Developed by Pascal Naidon and Patrick Corrieri
License: Open Source
OpenToonz is a more advanced animation tool that offers extensive features like audio import, scripting support, and a comprehensive timeline, making it suitable for professional animators. In contrast, Pencil is lightweight, user-friendly, and ideal for beginners, but lacks advanced features and capabilities found in OpenToonz.