Free OCR is a document scanning software including the Windows compiled Tesseract free ocr engine also known as a Tesseract GUI. It includes a Windows installer and It is very simple to use and supports opening multi-page tiff documents, Adobe PDF and fax documents as well as most image types including compressed Tiff's which the Tesseract engine on its own cannot read .It now can scan using Twain and WIA scanning drivers.
The Tesseract OCR PDF engine is an open source product released by Google. It was developed at Hewlett Packard Laboratories between 1985 and 1995. In 1995 it was one of the top 3 performers at the OCR accuracy contest organized by University of Nevada in Las Vegas. The Tesseract engine source code is now maintained by Google and the project can be found here: http://code.google.com/p/tesseract-ocr/
FreeOCR is a freeware document scanning software and you can do what you like with it including commercial use. The included Tesseract free OCR engine is distributed under the Apache V2.0 license.