Foundryside (The Founders Trilogy, #1)

by Robert Jackson Bennett

That was how the Scrappers got started. If you needed a lock fixed, or a door reinforced, or a blade altered, or if you just wanted light or clean water, the Scrappers would sell you rigs that could do that—for a fee, of course. And that fee was usually pretty high. But it was the only way for a Commoner to get the tools and creature comforts reserved for the campos—though the quality was never totally reliable.

It always bothered me that the wizards in Harry Potter never had an intellectual property system. This is the logical endpoint of that: a bunch of punk, underground hacker/wizards who are trying to reverse-engineer spells.