We all remember a day when Apple would charge heavily for its desktop software - Leopard specifically.

Now that's all changed, perhaps because of pressure from Microsoft and other companies. Last week Apple announced that Mavericks, its latest version of OS X,  would be available free from the Mac App Store. It was unclear if this non-pricing structure would stick for the company's software line but now Apple has cleared it up. 

CFO Peter Oppenheimer revealed on Monday that customers won't ever again have to pay for a new version of OS X. Like the just released Mavericks, all future versions of OS X will be free, the executive told investors on Apple's FY13 Q4 earnings call. 

Along with OS X, Apple has also begun to give away versions of iLife and iWork to users.

Apple CEO Tim Cook gave reasoning for free software to investors on the call: “"We are turning the industry on its ear. Some other folks charge $199 for each of these... the OS and the productivity apps. We wanted to make it a part of the experience.”

Free software will come at a cost, however. Oppenheimer told investors Apple will need to defer $900 million in device revenue to pay for the software - specifically $15 - $20 per iOS device and $20 - $40 per Mac.

"We are now making iPhoto, iMovie, Pages, Numbers, and Keynote available as free downloads to customers who purchased new iOS devices. We are also making Mavericks and future updates free to our Mac customers," Oppenheimer said. "As a result of these additional rights and features, we are deferring a greater portion of sales of each iOS device."