Students enrolled in approved educational institutions can access the Studio Educational Edition

Synfig is the closest open-source alternative to CelAction’s puppet-based system. It uses vector layers and skeletal deformation for smooth animation without drawing every frame.

If you see a link promising a "CelAction 2D full version free download," It is almost certainly a trap.

CelAction2D is an industry-leading tool used for hit shows like not available for a permanent free download

Cracked versions often crash frequently, refuse to save projects, or produce corrupted animation files. Losing weeks of work is not worth the "free" price tag.