Is there any open source software that will convert jpeg to word or rtf or just plain text
As noted in the comment on your question, it sounds as if you're looking for OCR (Optical Character Recognition) software. You could look at using Tesseract OCR -- it requires a TIFF file as input and outputs plain text, but you can easily call it from a script that converts the input from JPEG to TIFF and the output from plain text to whatever you want. Another option to consider would be GOCR.