Earlier this year, Apple instituted a program that enables accessory makers to put a "Made for iPod" logo on their products, in exchange for royalty payments. Likened to an "iPod tax" by some, the program is now mandatory for companies that want to connect their products to the dock connector on the bottom of the MP3 player, according to a CNET article.

Apple senior vice-president of marketing Phil Schiller told reporter Ina Fried: "Yes, the electrical connection has specifications around that and licensing around that, and the way you get that assistance and information and licensing is through the 'Made for iPod' program." He wouldn't say when the program became mandatory, nor would he say what Apple will do if a company decides to ignore the requirements.

Ms. Fried cited a source who told her that Apple charges a royalty of 10% of an iPod add-on's wholesale price. She noted that the market for such accessories is estimated at hundreds of millions of dollars annually. Piper Jaffray analyst Gene Munster told her: "Ultimately Apple is tired of watching these people profit off their success."

On the upside, Ms. Fried said that the "Made for iPod" program gives these companies "some peace of mind ... in knowing that the accessories they make today will work with the iPod of tomorrow." Mr. Schiller told her that Apple ensures manufacturers that their add-ons will work with future versions of the iPod, thanks to its pledge to include an adapter with the MP3 player. The iPod nano comes with an adapter that enables it to connect with devices designed for earlier editions of the MP3 player.

However, as Ms. Fried pointed out, the latest iPods have dropped the topside connector that many accessory makers used to rely on for their products. Now third party manufacturers have to connect their devices to the dock port, which has rendered a large number of accessories completely incompatible with the new generation of iPods.

"It's the key to the kingdom," Digital Lifestyle Outfitters vice-president Andrew Green said of the dock connector. He told Ms. Fried that his company is focusing all of its recent development work on products that use that port, a move all iPod accessory makers now have to make.