This is where I read the K20/Fit swap (which was done by HASport):
2007 Honda Fit K20 Install - Sport Compact Car Magazine
When you read this, it will make more sense. Hondata won't offer the jumper harness (unless demand is high enough), but they should be offering the K-Pro for the Civic Si. The engine they used in the swap was an '06 Si engine. The engine ran fine on the K-Pro, but the dash didn't work, which is why they needed the Fit's ECU. So Hondata has the code cracked, but they just don't have it for sale yet.