In an attempt to halt the unauthorized use of its digital assistant on devices not intended to run the software, Apple covertly instituted a "SetActivationToken" property list file which effectively disables any attempts to communicate with Siri's servers, according to Apple blog Redmond Pie.
To get the voice-recognition software to work on other iOS devices, the so-called jailbreak community came up with a basic program called Spire which installs the required on-device files to communicate with the Siri servers. Spire's developers, the prolific hacker "chpwn" and Ryan Petrich, allege that the program is a completely legal port.
The software has caveats, however, as it is only available to jailbroken devices, requires a proxy Siri server and an iPhone 4S certificate.
Despite the troublesome task of installing and troubleshooting the workaround, the demand from users who don't have an iPhone 4S yet want a taste of Siri has been enough to warrant a response from Apple.
Since Siri was announced in October 2011 as the standout feature of Apple's iPhone 4S, users of other iOS devices like the iPhone 4 and 3GS have questioned the company's decision to keep the software locked to the newest generation handset.
Apple has not officially responded outside of saying that the hardware on the 4S makes Siri possible, though previous anecdotal reports have claimed that the exclusivity may stem from a modified proximity sensor or integrated noise reduction tech from EarSmart.
The feature has been seen as a driving force for sales of the newest iPhone, and Apple may be pushing users to upgrade rather than rely on an untested, unauthorized piece of software.
The jailbreak community is already claiming that a simple "solution" to the "SetActivationToken" addition is to simply delete the entirety of a certain .plist information bundle, however the technique hasn't been fully vetted.
This latest attempt to free an iOS feature from Apple's "walled garden" is but one of a myriad jailbreak attempts by users who want interface with their devices in ways frowned upon by the company.