It has to do with Generally Accepted Accounting Principles (GAAP) financial measures. Because the way Apple was reporting its revenues, it was forced to charge

It has to do with Generally Accepted Accounting Principles (GAAP) financial measures. Because the way Apple was reporting its revenues, it was forced to charge for iPod touch software upgrades while it didn’t have to do so for iPhones software upgrades. That situation has since changed[1][2] and apparently, Apple has now found a way to make OS X upgrades free while adhering to accountancy rules. [1] http://tech.fortune.cnn.com/2009/09/14/accounting-rule-change-in-apples-favor/ http://tech.fortune.cnn.com/2009/09/14/accounting-rule-chang... [2] http://www.zdnet.com/blog/btl/apple-earnings-a-heads-up-on-accounting-change-would-have-been-nice/29947 http://www.zdnet.com/blog/btl/apple-earnings-a-heads-up-on-a...