yes.

it's one thing to look at a design and have it spark an idea, but when you just copy the design, and change it just so it'll be 'different' you're still just ripping off the design.

some things are harder to prove than others - some things just aren't the unique - but when you reverse engineer a design you shouldn't be paid at all. in actuality, it'd probably destroy your practice. it probably wouldn't be as big a deal if you knocked off one no-name template for another. it's still ethically wrong, but the time/money needed to peruse these isn't worth it to some kid who wants his $200 back - that might buy you a simple meeting with a lawyer.

if you're dealing with established business where their name is vulnerable to your actions, if you screw up, they'll come down on you as hard as they possibly can to keep their name clean of you.