The release comes just a day after Apple blocked a previous version of the program, called PyMusique, in part by requiring all iTunes customers to use the latest version of Apple's software.
In a blog posting, Norwegian programmer Jon Johansen, who was previously responsible for releasing software used to copy DVDs online, said he had been successful at reverse engineering the latest iTunes encryption.
Cody Brocious, a Pennsylvania high school student working with Johansen, said they saw the project as "necessary for the Linux community," despite Apple's opposition.
The programmers' work has been one of the most persistent projects targeting Apple, whose iPod and iTunes Music Store have drawn consistent attacks and experiments by people eager to extend the capability of the products, or simply disarm copy protection.
The cat-and-mouse response is a familiar one in the technology world, as programmers have often sought to write software compatible with larger or more popular applications. Instant messaging companies such as America Online, Yahoo, Microsoft and Trillian have long feuded, blocking and reopening access to each other's software.
The PyMusique programmers say they are primarily interested in allowing people using Linux computers to purchase music from the iTunes store, explaining their goals in a blog posting online. Their software requires users to have an iTunes account and pay the ordinary price for music.
They say they weren't aiming at creating a tool for stripping iTunes copy-protection off songs. However, Apple's system adds the layer of copy-protection inside the iTunes software itself, and so they didn't need to add it in their own version, they said.
Apple's software already allows customers to create an unprotected version of a song, by burning an iTunes purchase to a CD. That file can be ripped into an ordinary MP3.
While Apple has made no public legal threats against the programmers, the iTunes terms of service bars the use of any unauthorized software to access the store. Copyright lawyers have previously said that the PyMusique system, which evades Apple's intention to wrap all purchases in copy protection, may well cross legal lines.
"The work I do is completely legal in my country," Johansen said in an e-mail interview. "Of course, I know very well that not doing anything illegal doesn't mean you won't be prosecuted (or) sued."
Johansen was prosecuted in Norway for releasing the DeCSS code in 1999, but was ultimately cleared of charges.
An Apple representative could not immediately be reached for comment.
Brocious said the updated version of PyMusique would only be available for Linux, and that the programmers would not make a Windows version this time.