Mobile phone developers are scrambling to ensure that the openness of the Linux operating system does not anger telecoms regulators.

Consumers who run Linux on a PC are used to having full control over the operating system, but should not expect that same level of control on a Linux powered mobile phone, warned Mike Kelley, senior vice president of engineering at PalmSource.

The company is in the process of developing a Linux version for mobile phones to replace its current Palm OS.

"Phones are not PCs. They tie in to a radio that is regulated," Kelley said at the LinuxWorld conference in San Francisco.

"They are tied into very expensive back-end infrastructure that can be seriously disrupted by malfunctioning phones.

"[End users] wreaking havoc with what the phone does costs operators a lot of money. It could create security problems. It could bring down the cellular network."

Programmers have mostly focused their hacking efforts on removing so-called SIM-locks that bind a handset to a specific network.

The knowledge of the Linux operating system among open source developers, however, will significantly broaden the group of programmers with potential access to the devices.

Open source advocate Harald Welte, for instance, has successfully swapped out the 2.4 Linux kernel on his Motorola A780 for a 2.6 kernel.

Developers could also break into the phone to change the user interface, crack digital rights management technology or enable services such as roaming or wireless data to which they do not subscribe.

Regulators will get involved when developers start altering the operation of the radio.

Developers could seek to improve a handset's reception by boosting the signal strength, or instruct the radio to increase the frequency at which it contacts the cellular transmitter. Either could lead to a disruption of the mobile service.

"There will be some phones where being able to re-flash the phone gives you the capability to become FCC non-compliant. Therefore, the device manufacturers would make it extremely difficult to do that," said Kelley.

Karsten Homann, vice president of professional services at Trolltech, told vnunet.com that he expects mainstream phone manufacturers to lock down their handsets.

The company offers a software development kit that lets programmers create applications for Linux phones.

Current Linux phones have a separate processor for applications, which effectively throws up a physical barrier. Linux phones could also use a so-called 'sandbox' for applications, again separating the software from the phone's main functions.

Motorola is blocking all outside or native Linux applications on its phones. The company does allow its users to install Java software, which restrictions ensure network health and interoperability.

The biggest risk, however, comes from phone in regions with limited regulatory oversight, according to Homann.

"With Linux it's easier to make a phone that misbehaves," he said. "As it becomes easier to install applications and download data to a mobile phone, you will get the same issues as on the PC."