1. Are there TWAIN drivers provided for the Neat Receipts scanner to work in Mac OS X 10.5 (as a universal binary) and Windows?
NEAT Receipts for Mac ships with an Image Capture driver, rather than a TWAIN driver. The Windows version does not currently ship with a TWAIN driver either.
2. Can I use the Neat Receipt software with my Pentax DSmobile 600 USB (TWAIN compatible) scanner in Mac OS X 10.5?
You may be able to access the scanner using the Image Capture TWAIN Bridge, but we don't yet officially support any third party scanners.
3. How can I purchase Neat Receipts without the scanner?
Currently I don't believe that NEAT Receipts for Mac is available without the scanner, but this may (or may not) change as we officially support third party scanners.
Hopefully that answers your questions. We apologize if they weren't the answers you were hoping for, but the product is still very young and will grow more feature-ful over time.