Vectorize is a free, open source image tracing plug-in for Rhino.
If you are using either Rhino 8 or Rhino 7, use Rhino's PackageManager command to install the latest version.
Vectorize is licensed under the terms of the GNU General Public License, version 2 (or, at your choice, a later version).
Vectorize uses the famous Potrace by Peter Selinger, whose application transforms a bitmap into a soft, scalable image made up of vectors.
For Rhino 6, download the installer (below). Then double-click to launch the Rhino Installer and install the plug-in.