There is one fundamental difference. We consider a personal project any kind of project that does not imply remuneration, either direct or indirect. On the other hand, if you are seeking to be compensated for your design work, you are dealing with a commercial project. Work for non-profits or ONGs is also considered commercial work. Licensing is a complicated process, but we do our best to make it as easy as possible for you. To clarify any doubts, please visit the general license page or the font-related one.