I suppose the interface might be covered by design patents, which are sort of like trademarks. I doubt it would be covered by a utility patent unless there was

I suppose the interface might be covered by design patents, which are sort of like trademarks. I doubt it would be covered by a utility patent unless there was something really unusual about the interface. At any rate, patents expire after 20 years, and trademarks do not. Copyright could theoretically come into play, but I think the "look and feel" lawsuit pretty much established that it's pretty darned hard to enforce any kind of copyright on a user interface. Some of the very old synths that Behringer has been cloning were probably protected by utility patents that covered the electrical circuits, but those have long expired, and I think trademarks become unenforceable if your aren't actively selling a product that uses it anymore. I don't have any moral objection to cloning the old synths either -- our laws have mechanisms to grant inventors exclusive use of their ideas for a limited time, but when that expires it's part of the commons. That's a good thing. I do think it's gross though to clone a popular recent synth just because you can and because the original designer didn't file the right paperwork to stop other people from doing that. There's a continuous flamewar on /r/synthesizers between the people who think Behringer is a detestable parasite and the people who think they're making high-quality analog synthesizers available to the masses in a way that they never have before. I think both camps are right to a degree. I will defend Behringer's right to use the stuff that's clearly in the public domain, but I also think they have no class. They do things that damage their reputation even when it wouldn't have required much effort not to. (I'm not an IP lawyer, so don't take this as expert commentary.)