[UPDATE (Oct 14, 2010): HTC has released the source code. Evidently 90-120 days was not in fact necessary, given that they managed to do it 7 days after the phone’s official release. It is possible that the considerable pressure from the media, modders, kernel copyright holders, and other kernel hackers contributed to the apparently accelerated release.]

[UPDATE (Nov 10, 2010): The phone has been permanently rooted.]

Last week, the hottest new Android-based phone arrived on the doorstep of thousands of expectant T-Mobile customers. What didn’t arrive with the G2 was the source code that runs the heart of the device — a customized Linux kernel. Android has been hailed as an open platform in the midst of other highly locked-down systems, but as it makes its way out of the Google source repository and into devices this vision has repeatedly hit speedbumps. Last year, I blogged about one such issue, and to their credit Google sorted out a solution. This has ultimately been to everyone’s benefit, because the modified versions of the OS have routinely enabled software applications that the stock versions haven’t supported (not to mention improved reliability and speed).

When the G2 arrived, modders were eager to get to work. First, they had to overcome one of the common hurdles to getting anything installed — the “jailbreak”. Although the core operating system is open source, phone manufacturers and carriers have placed artificial restrictions on the ability to modify the basic system files. The motivations for doing so are mixed, but the effect is that hackers have to “jailbreak” or “root” the phone — essentially obtain super-user permissions. In 2009, the Copyright Office explicitly permitted such efforts when they are done for the purpose of enabling third-party programs to run on a phone.

G2 owners were excited when it appeared that an existing rooting technique worked on the G2, but were dismayed when their efforts were reversed every time the phone rebooted. T-Mobile passed the buck to HTC, the phone manufacturer:

The HTC software implementation on the G2 stores some components in read-only memory as a security measure to prevent key operating system software from becoming corrupted and rendering the device inoperable. There is a small subset of highly technical users who may want to modify and re-engineer their devices at the code level, known as “rooting,” but a side effect of HTC’s security measure is that these modifications are temporary and cannot be saved to permanent memory. As a result the original code is restored.

As it turned out, the internal memory chip included an option to make certain portions of memory read-only, which had the effect of silently discarding all changes upon reboot. However, it appears that this can be changed by sending the right series of commands to the chip. This effectively moved the rooting efforts into the complex domain of hardware hacking, with modders trying to figure out how to send these commands. Doing so involves writing some very challenging code that interacts with the open-source Linux kernel. The hackers haven’t yet succeeded (although they still could), largely because they are working in the dark. The relevant details about how the Linux kernel has been modified by HTC have not been disclosed. Reportedly, the company is replying to email queries with the following:

Thank you for contacting HTC Technical Assistance Center. HTC will typically publish on developer.htc.com the Kernel open source code for recently released devices as soon as possible. HTC will normally publish this within 90 to 120 days. This time frame is within the requirements of the open source community.

Perhaps HTC (and T-Mobile, distributor of the phone) should review the actual contents of the GNU Public License (v2), which stipulate the legal requirements for modifying and redistributing Linux. They state that you may only distribute derivative code if you “[a]ccompany it with the complete corresponding machine-readable source code.” Notably, there is no mention of a “grace period” or the like.

The importance of redistributing source code in a timely fashion goes beyond enabling phone rooting. It is the foundation of the “copyleft” regime of software licensing that has led to the flourishing of the open source software ecosystem. If every useful modification required waiting 90 to 120 days to be built upon, it would have taken eons to get to where we are today. It’s one thing for a company to choose to pursue the closed-source model and to start from scratch, but it’s another thing for it to profit from the goodwill of the open source community while imposing arbitrary and illegal restrictions on the code.