Are hobby projects with monetization potential considered "outside employment"?

I am attending grad school this fall in engineering. I've been reading the graduate handbook, and it states that working as a research assistant (20 hours a week) constitutes a full-time job and outside employment is not allowed.

However, in my free time (for entertainment), I have lots of little programming projects I've been working on. Some are simple mobile apps; some are large web applications. If I began making money off of any of these projects, would that constitute "employment"? Note that I'm not working with anyone but myself, and I don't plan on becoming a business any time soon, so I'd like to think of it as "hobby that makes a few bucks", but I want to be sure. Also important is that none of this would interfere with my school work; as weird as it sounds, programming is a relaxation activity for me.

I'm a little bit hesitant to ask the school about it, because it may come across wrong and I'd prefer to keep my personal life independent of my research activity.

What do you all think?