Used to be that you trademarked your logo and your model-name. But trademarking your colors, shapes, etc. is ridiculous. How is this different from Toyota AND Honda selling yellow cars? If it looks like a Fluke, and I pick it up and see SparkFun on it, I think, "Heh, they copied Fluke's design". It's not disingenuous. They're selling an inferior product for a much smaller price to people who don't need a $3000 Fluke meter to check their robot's power relay. They're not labeling it or branding it as a Fluke. How does this harm Fluke's IP?