Hi I am Andrew Sheridan, co-founder of the i4Siri. Currently we are working hard on a Siri port for people who do not own the iPhone 4S. We plan to do this via a siri proxy/server that will handle siri requests just like apple. We plan to do authorization via UDID and do away with iPhone 4S Auth keys.
As for the legality of the port we have a plan. We plan to release a program for your computer (windows and mac) that will extract the siri files from a iPhone 4S ipsw that is on your computer then it will ssh the necessary files to your iPhone. This is a dumbed down idea of it but you should be able to get the point. After running the program a final step will include running a package in cydia on the i4Siri repo that will install a mobile substrate plugin that will install authorization.
Co-founder @leftyfl1p and I hope to be able to release this port soon however there is no ETA. We hope to be able to release the utilities necessary for people with an iPhone 4S very soon. As for people without a 4S we hope to be able to buy the server and have everything fully functional by the end of the week.
Our last post got spotted on Mashable along with many other technology sites. We have currently raised a decent amount of money and will be investing it into servers for the port. If you would like to donate you can here.
Make sure to check back on Jailbreak Nation for updates via the developers.
The video below shows off a demo of custom commands on the proxy server: