If you want to see a completely original UI with not a single thing "borrowed" from elsewhere, my 5yr old has some drawings to show you.
This specific case takes it too far, there's no doubt about that. But you can be sure that the Trello designer was heavily influenced by those that came before him. UI designers spend half their time looking at UI's designed by others to see what works and what doesn't.
In fact, more often than not, UI design should be copied. You don't design a completely different light switch just because you want to be original. Function before form.
Of course the cross-pollination is required. But this LibreTrello thing is a blatant rip - the look and feel, the semantics and interaction flows, all the details. Everything, to the dot.
It's still would've been not a big deal if it were just a temporary placeholder design and it got released to the public accidentally. Gotta start somewhere, that's understandable. But they act entitled to what they did. This is what the problem is. They don't recognize or acknowledge all the work that Trello devs did to get things where they are. And they did a lot of it, which is plainly obvious from the fact that there was no other Trello before them.
This specific case takes it too far, there's no doubt about that. But you can be sure that the Trello designer was heavily influenced by those that came before him. UI designers spend half their time looking at UI's designed by others to see what works and what doesn't.
In fact, more often than not, UI design should be copied. You don't design a completely different light switch just because you want to be original. Function before form.