The "Project Owner" refers to the person that has last edited a Project.
If you have duplicated a Project, or one has been shared with you, and you continue to edit and/or change it in any way, this Project has now become yours, once opened in the Animatron Editor.
Since you have opened the shared or duplicated Project in the Editor, this new version is only accessible from your very own Account Gallery, making you its Owner.
Once you share this Project with someone else to continue editing, they have taken your place as the Owner of that version of the Project, since it is now only accessible from their Account Gallery.
Note: The Project Owner is NOT the same as the Original Author of a Project. The Original Author is the person who first created the Project that is being viewed or edited.