Try these free alternatives – sometimes a bit rougher than the commercial packages, but the price is right and the features are all there.
• Pencil – has been written by animators for animators. It has one of the best user interfaces for hand-drawn animation in the computer. The original developer has since forked this to open source.
• KToon – Adventurous Linux users may wish to try this package. KToon has had a rough time – it appears to be a fairly well-designed piece of software, but it has floundered in development. One fork, called Tupi, seems to be somewhat healthy.
• Synfig – Synfig is aimed at the vector artist, but designed for animation, not web banners. An influx of cash and a Kickstarter seem to have breathed new life into a great project that needed some attention.
• Blender – is an open-source 3DCG environment that can produce sophisticated, professional results. There are loads of free tutorials, content, plugins, and extras for Blender, plus great support for practically any platform.
• Make Human is a project designed to create realistic-looking 3D human models. It is an open source analog for Poser.
• StopMojo is a Java-based animation program designed for stop-motion. It can also be used for pencil-testing animation drawings.
• These days maybe all you need to do stop-motion is a DSLR and a copy of Entangle
• Then there is Linuxstopmotion.