I have been writing a system that partially satisfies the notion
of "Open Source Paperport Equivalent".
I have been writing a system that partially satisfies the notion of "Open Source Paperport Equivalent".But it does a lot of things that I don't think Paperport does. For instance, it has automatic document classification, syncs with your filing cabinet, has date extraction and fills a calendar with date mentions for easy checking of due dates, has semantic web integration and can do a lot of sophisticated natural language processing, such as extracting todo lists from documents, spam detection, urgency classification, along with planning, scheduling and execution features. (You can set due dates, and document and task interdependencies, i.e. this document has to be sent to so and so and a reply received before we can fill out this document). So it has workflow support.
There are many more options and plans for this system than are easy to reveal at this moment.Much of the way it handles documents will be similar eventually to KBFS. It can be used to maintain the reading lists for CLEAR and Study. It will integrate with SPSE2 and PICVis when they are complete enough to represent various domains. It may even merge somewhat with them.