The overall look and feel of an application can't be copyrighted. Images like the Firefox logo can be copyrighted, and names like Red Hat can be trademark. If you want to make an OS that looks like android you are free to do so. KDE used to include a theme called Redmond that copied the look of another desktop, and another theme called Baghira that looked like Aqua/OSX. If you want to use Android source code, then you'd have to agree to their license, which IIIRC is an MIT license, which basically you have to give credit to google for their source code.
Anyways, the thought of Google giving Apple a taste of their own medicine would be absolutely delightful.
These days, it does not really matter what can or can't (should or should not) be done. All you need is a lawyer and lots of cash and you can drag anyone into court for "violating copyright" because your GUI looks like my GUI.
There are no shortages of 'Look and Feel' lawsuits; they are as old as the computer business. Something might not be properly protected (patents, trademarks, service marks, etc) but that does not stop the lawsuits from happening. Something might be wrongfully protected and you win when you should not win.
These combatants go to court, win their cases and then later, they loose on appeal. When Apple wins, they are the bad guys; when they loose, the world claims they should have lost when in reality, they should have won.
The current patent/trademark/copyright issues are a complex mess and something needs to be looked at.
People do not understand how it works and how it works often defies explanation. Consider that you cannot protect the title of a book or consider that I can manufacture and sell clothing with Disney characters and without permission of Disney. Before you comment, carefully consider what I said about Disney, Smiley.
Nothing is as simple as many on the net seem to think. Apple is often chided for suing or seeking injunctions in court about issues many casual observers think silly or unfair. Fact is, you must actively protect your IP, and it is not wrong to do so. and yes, some patents are issued that should not be issued.
L and F lawsuits are a serious issue because they can be used to hamper business. Sometimes I think it is less about legitimate issues and claims and more about how much cash you have to stop any competitiveness.