Usually they've caved in to the conventions of the market (iOS notifications) or missing features (F.lux). The amount of blatant theft seems minimal. They usually put their own spin on things to differentiate somehow.

Even Microsoft has gone its own way with Windows after some heavy overlap with MacOS and other windowing systems (DESQview in partcular). Windows 3.1 was more different, and Windows 95 borrowed more heavily from OS/2, which was wildly different from MacOS. If anything Apple was forced to adopt the right-click menu popularized by Microsoft since it became the de-facto standard.

Meanwhile other companies have damning memos that say "Make it look exactly like Apple's product".