Just so you know, if you plant an apple tree from an apple you buy at the grocery store you will likely be sued for patent infringement. Though, it's probably sterile anyway.
But your planting of a tree doesn't automatically prevent the farmer you bought the apple from from making any money.
If I have to release my code under GPL, I can't make money charging thousands for it (low volume type of app). If I can't make money from it, I won't spend years developing it. Not having the app would make it harder for some pharma scientist somewhere to cure cancer. Everyone loses. Communism doesn't work.
You are not forced to release your code under the GPL. You can spend years developing it and release it however you want.
However if you choose to release under the GPL you will be standing on the shoulders of giants. You will have whole new avenues of development opportunity opened up to you as a result.
"Communism" does work in the sense of the Linux ecosystem that you see around you every day. Not only that, but companies like Microsoft are forced to innovate because open source eventually catched up to them. Without free software all software would be tied up in a morass of patents and licensing fees. Progress would have ground to a halt, and we would wait with baited breath to pay $500 for the latest version of Windows crafted upon their latest business model to coerce upgrades from all their regular customers.
If you are adding 1000 man hours on top of 50,000 man hours of development that you are getting for free, is it moral for you to give nothing back? The GPL is simply a way for the contributors of the 50,000 hours to say that you can use their code if you share in return. It's not clear at all why you think you should be entitled to that code.
you're legally allowed to use it to grow yourself an apple tree.
Legally, sure (modulo plant patents). Practically, you can only do it as long as you don't mind it being a crab apple tree. (Apples tend not to breed true; if you want a tree that is sure to produce edible apples you have to get it by grafting.)
I assume you didn't mean free in some other way, right?