OK so I have downloaded and tested ribsu
First of all, let me tell you I'm not a developer so my feedback will be limited to confirming it runs and basic functionality. Also if i state somenthing thats obvious or plain stupid I escuse myself by just arguing ingonornace
My Setup:
Mac Mini rev-b
1.42 Ghz G4
512 Ram
Running Tiger (Mac OS X 10.4.2)
I Connected USB-UIRT and checked to make sure the USB port saw it.
I ran ribsu in Terminal and tested a couple of the commands
20 UIR
Everythin OK tested a couple of IR Signals and got back 6 Byte codes OK
21 RAW
tested a couple of IR signals and got 36 codes back, copied and pasted and codes were sent out OK.
If I leave button pressed on remote the reapeating 36 code is one more shorter that original (guess its a repeat code) whch alone will do nothing if pasted back.
I did manage to paste garbage a couple of times

and got the eror codes 80 or 81 back.
24 RAW2
Nothing happens with this mode, did not react to any codes I tested from remote. Is RAW2 supposed to react just to certain protocols?
First time I tried quiting I typed quit instead of just Q and USB-UIRT got stock with led ON all the time, I just unpluged and plugen again and evrything back to normal.
Regarding API and furhter development, what would be great and give the best flexibilitywith a simple interface would be to have just a backround app running that understands Apple Script and very basic GUI to output learned code (like right now with 21 code).
So you could just script to it like:
Tell Application ribsu
send code '36192739812749164981'
end tell
There are lots of applications that can trigger an Apple Script based on several events (like X10, Keyboard, other USB input, etc) so off the bat you could have USB-UIRT integrated and working
Now in terms of reacting to received IR codes (UIR) not sure how to trigger a response from this basic app idea, could be hte app launches an apple script itself in response maybe?
Hope this feedback helps in some way.
UR The Man !