People often conflate proprietary software with commercial software, believing software can only be sold if it's proprietary, because a proprietary license is the only thing that prevents people from using software without paying.
In fact that is not the case at all. On the one hand, proprietary software is used all the time in violation of its license, as the industry's own figures demonstrate.
So clearly proprietary licensing is no guarantee of payment, therefore the license itself is irrelevant to selling software for profit.
But again, the GPL is also no guarantee of payment, in fact it has the additional benefit of allowing people to use GPL-licensed software at no cost without breaking copyright law, even though copyright law is clearly not an effective disincentive to use software without paying, as demonstrated above, and is thus a moot point.
So one way or another, licensing has no bearing on whether or not people choose to pay for software, therefore there is no reason to choose a proprietary license for your work, and you'd be just as well publishing it under a Free license. This will then provide many other benefits to many people, including you - the author, such as collaboration, bugs and security auditing, architecture support, and the contribution of your knowledge for the common good, rather than holding it hostage for ransom, in a futile attempt to force people to pay for it. You'll still get paid, mind you, one way or another, just not for "IP".
But certain people apparently still don't understand, or don't believe, or don't want to believe that knowledge-based products can be sold without restricting the dissemination of that knowledge with proprietary licensing. They persist in believing they can magically "force" payment with a license, even though this theory has been disproved over and over again. They simply cannot envision any circumstances where people would pay for something that they can obtain elsewhere for free, even though people do in fact obtain proprietary software elsewhere for free. Bizarre? Yes.
Well, perhaps this analogy will help them to understand:
Consider a simple grocery product like, say, tomatoes.
There are two main ways to obtain tomatoes: buy them in a shop or grow them yourself. If you grow them yourself there's some initial expense: a cold frame, seeds, fertiliser, bamboo canes, etc., but thereafter you can essentially grow your own tomatoes for free ... forever, by simply cultivating the soil and harvesting seeds from each previous crop.
Many people do in fact grow their own tomatoes, and I'm fairly certain that even the most hardcore "IP" fanatic would not describe such people as "freetards" or "pirates" or "thieves" or "communists".
So why hasn't the tomato industry gone bankrupt?
Because most people choose to buy tomatoes rather than grow them, even though there is nothing to stop them doing so. People buy things because its more convenient than the DIY method, because the commercial product provides some form of "added value" that appeals to customers.
But people still have the freedom to "do it themselves" if they want to.
That is Free Software.
Free Software is simply a reflection of the normal state of the Free Market, where consumers have the option to either buy a product made by one company, or another company, or do it themselves. Just like Free Software can be bought from one company, or another company, or you can "grow" it yourself from the freely available corresponding sources. This condition applies to nearly every product on the market.
Except certain knowledge-based products, like proprietary software.
"Intellectual Property" sticks out like a sore thumb in the world of commerce, because it's unnatural, unlike any other product. It doesn't conform to the proper rules of property ownership and the legal exchange of goods by payment. It's an abomination. Nobody understands it, nobody likes it, and (according to the above figures) about 60% of the population just choose to ignore it.
People will pay for software, for the same reason they pay for tomatoes, because it's more convenient than "doing it themselves".
Others won't, for a myriad of reasons, of which cost is just one. Some people prefer autonomy, as and when it's practicable. Some people prefer specialist items, which are simply too "unpopular" to be commercially viable. Some people just enjoy DIY as a hobby.
But whatever the reason, there will always be a sufficient number of people who prefer to rely on the commercial provision of products, and it really doesn't matter to them what the "license" is, if any. They don't buy tomatoes in a shop because they're licensed.
But customers are not the only concern for proprietary software developers. Their other concern is that, without proprietary licensing, competitors will be able to provide the same product, perhaps even improving it and/or selling it at a lower price. Proprietary licensing prevents such competition.
Yes it does.
However, this does not explain how, as per our analogy, competing producers are all able to sell essentially the same product, tomatoes, or any other real property, in the Free Market.
If they can do it with real property, then why can't software developers do it with knowledge-based products too?
Well, the answer is: of course they can, but they don't want to, because the essence of proprietary licensing is greed, not necessity.
There is in fact no reason knowledge-based products can't be sold in exactly the same way as real property, without licensing restrictions. People who prefer to "do it themselves" will do so irrespective of what the license states. People who prefer the convenience of commercial provision will buy goods, again irrespective of the "license", if any. The healthy market conditions that necessarily facilitate multiple providers of real property can equally support providers of knowledge-based products. There is no reason this cannot work, and indeed it has already been proven to work by the existence of commercial Free Software providers.
So why is this not a common business paradigm?
Primarily it comes down to dogma and greed. Market conditions that would not be tolerated in the world of real property, are the de facto condition in the world of knowledge-based products. "IP" rights owners have been granted an artificial privilege that is, in reality, a prop that supports an otherwise unsustainable and highly immoral business model. They're essentially sucking on the tit of state aid, and are reluctant to let go. They've lived with these de facto conditions for so long that they can no longer imagine any other way, and the Free Software business model seems alien and abhorrent to them.
And yet the Free Software business model works, just like the Free Market works, just like the sale of any other goods works. And unlike "IP", it works without subjugation. It just doesn't provide the protectionism of state sponsored monopolies.
Free Software is not the anomaly, it's not the odd one out, it's not some wacky "communist" doctrine that seeks to restrict commerce. It conforms exactly to the same principles as the rest of the Free Market.
The aberration is "IP". It is the anomaly, it is the odd one out, it is the "wacky" doctrine that seeks to restrict commerce. It contradicts the principles of the rest of the Free Market, and as such it should be abolished.