Siri has been ported over to the iPhone 3GS by @chpwn and @stroughtonsmith, as posted by Edmonton-based developer, @rpetrich, who is currently working on Activator integration.
Check out the video posted below by Ryan Petrich:
As @stroughtonsmith and I demonstrated a few days ago, it is possible to run Siri on iPhone 4 and iPod touch. However, as we are currently unable to distribute the port or the procedure we used, I think I should at least explain tthe reasons why that isn’t happening
For a little background information, it’s important to understand the fundamentals of how copyright law works. Apple owns the copyright on the software, images, and data used inside iOS: they created them. Because of that, they have the ability to decide what other people can — are licensed to — do with them: copy, distribute, adapt, modify, or any number of other protections of their works. Pretty simple. But this does lead to one important, if somewhat counterintuitive, fact: just because a piece of data is available freely on the internet does not mean that you have the rights to redistribute that data (or any part of it) without an applicable license. In practice, that means that just because certain files are freely available on a device or inside a firmware (.ispw) file freely downloadable from Apple’s website, it does not imply that those files can legally be distributed by anyone else.
As much as getting Siri on your non-iPhone 4S would be great, it will be piracy if it is widely distributed.