If you want to get nit-picky about it, Microsoft stole nothing either...
Stolen Quicktime code was found in Video For Windows, the apparent fix for inferior performance in the previous version. Apple had previously refused to license that code. As mentioned in the other posting, the investment of $150 million in Apple stock, removal of the Apple code, agreement guaranteeing continued updates to office, and Apple continuing to include Explorer for a short time were the major components of the out of court settlement reached.
Involving a third party in getting the code doesn't excuse using stolen code.
The earlier issues went beyond the look of an icon. The functional behavior of multiple windows was a major issue that I recall.
"QuickTime for Windows vs QuickTime for Video for Windows
Apple brought QuickTime to Windows by simply porting large chunks of the Macintosh's native drawing system. QuickTime performance on Windows was vastly better than Microsoft's Video for Windows because Apple bypassed the GDI Windows graphics subsystem.
Microsoft and Intel were both shocked to find that Apple could deliver smooth video on the PC that was beyond what either company had imagined to be possible. When Microsoft requested a free license for QuickTime for Windows in 1993, Apple refused.
Meanwhile, Intel wanted to accelerate Microsoft's Video for Windows in hardware. It approached Apple's partner Canyon to develop a video driver that would provide similar performance to QuickTime.
While knowing that Canyon possessed Apple's code, Intel did not specify that Canyon needed to do clean room development, and gave the company an unrealistically short timeframe to develop the code.
As expected, Canyon simply delivered Apple's code to Intel, which then licensed it to Microsoft. When Video for Windows suddenly improved in 1994, Apple investigated and found that Microsoft had simply stolen code from QuickTime in order to compete with QuickTime.
Apple sued and won an injunction that stopped Microsoft from distributing portions of the stolen code, and the case was eventually resolved as part of the 1997 agreement between the two companies."
Going to the Apple partner that had the Apple source code and ending up with it was not legitimate Windows innovation.