I would like to describe the situation as cheating in the game without trying to going down into the rabbit hole that the digital goods opened(or expanded, since before the digital era we already had goods that are valuable other than it's material and building value. Books, Paintings, Designs, Blueprints and more).
So, you are producing something with intention to gain money or maybe just reputation but often you already use other peoples work to do that - nothing is made out out of thin air.
Then somebody is building some other product with some intention like making money, gaining reputation or something else and his product is using your product and maybe many other people's products. Let's say a website with AI that awesomely curates the content of other people.
In this situation everybody produced a valuable product but the other guys product's success is on your expense.
Ideally you would have an arrangement where everybody wins.
I will give an example from the movies and music industries:
a)When you have the arraignment it's iTunes store.
b)When you don't have one, it's the Prate Bay.
or Defense industries:
a) When you have a contract it's joint venture and you exchange some information to build some product.
b) When you don't have one and you spy on each other to create similar product its espionage.
or personal relationships:
a) When a couple are also seeing other people with the consent of the other one, it's open relationship
b) If there is no consent, it's called cheating.
It's not about stealing, it's about managing the resources in coordination with other parties so that everybody wins. Otherwise often one party wins in expense of the other, many time everybody loses in the long run.