Curve Shapes is a Blender extension from Mad Pony Interactive that lets you manipulate geometry with curves. It uses Bezier and Poly curves to create clean topology, and those curves control the generated mesh in real time.
The extension is suited to building organic forms, including armature and muscles, and other shapes you construct from curves. Because the curves drive the mesh directly, editing a curve updates the resulting geometry as you work.
Curve Shapes supports Blender 4.2, 4.1, 4.0, and 3.6, and is released under the GPL license. Documentation and a demo video are available, and the developer follows the extension's development through community channels. It sits at rank 1366 in the superhive library. Check the developer's page for the current licensing details and the latest builds.