It's a bit more than just the layout - the colours and look and feel are almost completely identical.

Right, but they actually say that on their website!

Is that alright these days? If they're pals, fine, but otherwise?

It is definitely not alright. They must have permission. An acceptable looking ThemeForest template is a $20 cash outlay; who would risk their launch over this?

It's awesome if Square actually "loaned" them their design. That seems like a genuinely useful thing an established company could do for a fledgeling one.

Even then, it leaves them needing to adjust their branding/L&F at some point which may be jarring for users. Wouldn't be that difficult to borrow the best of the Square layout but use their own fonts, colour scheme, etc and have something of their own.