The word means non-professional. So you don't do it for a living. Which is directly factually a description of what's happening here.

In some contexts is could be negative, because the concept of a non professional doing the thing is scary. Like there's nothing positive about an amateur heart surgeon, or amateur parachute designer.

But in the context of gardening it's clear and descriptive. The needs of a professional farmer and someone with a backyard garden are very different. The term clears up which one this app is made for.