The FreeCAD logo has been selected by the FreeCAD community during a contest of proposals made by community members. It has then been donated to the FPA to be managed on behalf of the whole FreeCAD community.
The logo is a trademark owned by the FPA (FreeCAD project association). This means the FPA is the sole body authorized to set its license, that is, to say who has the right to use the FreeCAD logo or not. The logo files, which are part of the FreeCAD source code or available elsewhere, for example on this wiki, are still all under the same licenses as the rest of FreeCAD (LGPL for the source code and Creative Commons for this wiki). You are still free to use the FreeCAD logo anywhere, on the same terms as the rest of FreeCAD, which means, basically, that you must use it to reference FreeCAD, and not use it, for example, for your own product, or any other way that is not referencing FreeCAD.
The bottom line is, you are welcome to use the FreeCAD logo anywhere, but you should only use it to refer to FreeCAD itself, not to, for example, your own business.
The logo files in different formats are all hosted on the FPA Git repository. For your convenience, a logo kit (zip file) is also available for download, that contains all the needed files.
Together with the logo files, you will also find a convenient guide book that explains how to use the logo.