You should have a license clearly displayed. A LICENSE file in your github repo or selecting the appropriate license on a print sharing site like printables or thingiverse is sufficient.
The Voron project uses the GPL v3. The Ender 3 was also made availabe under this license as are most reprap based printers including the Prusa i3 series. It is recommended that you use this license as your work is likely to be a derivative of some of these projects.
The GPL requires you to provide your source files to anyone you provide object files to. This means you need to provide your original cad files. STEP files are a convenient interchange format but strip away useful information. It's preferred that you provide these as well, particularly if the original cad files cannot be opened with a free tool.
This registory does not police license compliance, nor does inclusion of links to a project certify license compliance or suitability for any kind of derivative work.