I know this is an old thread, but I'm trying to use the Eventbrite barcodes to check visitors in. @johndpope - did you get any further in your quest?
The codes on each ticket are not QR Codes, but Datamatrix (for reading by the iOS/Android app) and Code 128 (I think). Both codes on the ticket (and incidently, the QR Code on Conferencebadge.com's app) are simply numeric and take the following form...
{OrderID}{AttendeeID}{Seq}
for example
123456789 123456789 001 (no spaces)
Any bit of barcode generating code can recreate these, but checking people in without an API method is a bit harder. The iOS/Android app rightly uses HTTPS and you need to be authenticated to the website to use the checkin_update URL used by the website.