The free account allows data motion inside SelfCAD. That means you cannot export your design and download it to your computer.
The paid subscription gives unlimited access to all features within SelfCAD. Including intuitive UI, modeling and sculpting tools, deformations and modifications. You can export to 40+ formats, download 3D models, upload your work straight to MyMiniFactory account and your Facebook profile. You can upload any STL object and modify it. The paid subscription allows printing directly from the browser.