Is it "sour grapes" if I bring a big dish to a potluck to share and I get mildly irritated if someone walks over and takes the whole thing to their table, ensuring nobody else gets any of it? Is it fine if a crowd of strangers shows up to my potluck without bringing anything, takes all the food, and leaves? Should I be able to go to a food-bank-for-the-poor and walk out with a big crate full of food since it's free?
At some point you have to recognize that a lot of our society operates on the expectation that people will behave in accordance with norms so that we don't have to bake every single thing down into extreme rules and have them enforced by armed goons. You're certainly free to ignore norms and do whatever benefits you the most at expense of others, but if other people did that to you constantly you'd probably end up pretty grumpy. There are lots of ways you can inconvenience someone without breaking the law.
Personally, I gave away a very useful free software package for ~4 years that I maintained solo, and multiple corporations repackaged it to sell to people without ever contributing fixes. Then when I stopped maintaining it for free, they all sent me emails offering to sponsor it (at pathetic rates). Seems like my free labor was worth something after all!