There are so many ways to interpret professional... I've worked with so many permies and contractors in my time, and each has classed themselves as professional. Yet some gained 'professional' status by reading a book and surviving on wit for two contracts.
"Professional" is a very simple definition - do you make your living from writing software? If so, you're a software professional.
That doesn't imply you know what you're doing, of course. Just means you're SUPPOSED to.