Howard Stern said a contract "rights issue" is the reason why his show isn't on the Sirius XM (SIRI) software application that was made available last week at the Apple (AAPL) iTunes store.

"It was a rights thing, a contractual rights thing," Stern told listeners on his radio show today. "It was a rights issue and a whole entanglement thing. So, we're not on it. Maybe one day we will be."
Some iPhone customers were looking forward to Sirius XM's app because it would allow them to listen to Stern's show at their convenience through their phone. Angry fans wanted to hear Stern's explanation. Stern explained within the first 30 minutes of his radio show today, which is his first live show since the app was introduced last week.

His sidekick on the Sirius XM show Robin Quivers told Stern on the air, "A lot of people were looking for the app because they wanted to get rid of one device and have us on their phone." Stern agreed, adding, "Hopefully one day we will be on there."

Without Stern's show on the app, "It's like a product-light version," David Bank, analyst at RBC Capital Markets, told DailyFinance last week. That said, the Sirius XM app is the second most-popular free app being downloaded by iTunes users today, and has been the most popular download in the music category since its release.

Stern didn't say so, but likely his show falls into a category similar to the National Football League, Major League Baseball and Nascar, which also cannot be heard through the iPhone app because of contract restrictions. Sirius spokesman Patrick Reilly wasn't immediately available for comment when phoned today by DailyFinance.

The app is free to paying Sirius XM subscribers and does broadcast Playboy radio, which debunks the initial theory that Apple's app censors would have shot down the app because of Stern's mature content. Some media outlets, such as Bloomberg News, reported that last week.

"I was reading on the Internet that (our) show was too dirty," Stern said on his show today. "How can it be too dirty if you have the Playboy channel on there?"

Finally, could Stern be hinting that his days with Sirius XM won't extend beyond his five-year $500 million contract? While explaining that he enjoys other channels besides his own, he said, "Sirius is great, even without us."

Anthony Massucci is a senior writer for DailyFinance. You may follow him on Twitter at hianthony.