Fred R. Conrad/The New York Times

Apple’s free book-creation tool, iBooks Author , seemed too good to be true: it gives anyone the ability to easily lay out an interactive book with no programming required, slap it up for sale in Apple’s iBooks Store and ideally make a quick buck. But hours after Apple released the software on Thursday, people noticed that they were not allowed to sell these books outside Apple’s store.

That’s according to iBooks Author’s fine print, better known in the software industry as the end-user license agreement. It reads:

If you charge a fee for any book or other work you generate using this software (a “Work”), you may only sell or distribute such Work through Apple (e.g., through the iBookstore) and such distribution will be subject to a separate agreement with Apple.

In other words, Apple has indirect ownership of your iBooks, because you can’t sell them through anyone but Apple. The clause immediately provoked controversy on the Web, even from some of Apple’s biggest enthusiasts, like John Gruber, who runs Daring Fireball, a popular blog for Apple watchers.

“This is Apple at its worst,” Mr. Gruber wrote. He later published a follow-up post explaining that this rule was most likely designed to prevent authors from using iBooks Author to make e-books for competing digital book stores, like Amazon’s or Barnes & Noble’s. It would also ensure that Apple received its 30 percent of the cut for every e-book title made with iBooks Author.

But Dan Wineman, who first reported on the license agreement, compared this to Adobe telling people that they could not sell images they produced with its Photoshop software to a third party, like Getty Images.

Apple declined to comment.

In the technology world, the end-user license agreement is known as the stuff that hardly anyone reads before clicking “Agree.” Written by a company’s lawyers, these agreements occasionally contain curveballs that people wouldn’t expect. For instance, after Sony’s PlayStation network was hacked in 2011, it updated its EULA to include a clause saying that people could not put together a class-action lawsuit if their personal information was stolen.

Apple has been notorious for imposing strict rules on its software and platforms. In 2010, the company prohibited programmers of iPhone apps from using third-party tools to make their software; iPhone apps had to be created with Apple’s approved tools. After this stirred debate, Apple lifted the restriction.