Looking for an open source library, for C++, Java, C# or Python, for reading the data from Quicken .qdf files.
@Swati:  Quicken .qif format is for transfer only and is not kept up to date by the application  like the .qdf file is.
QDF is proprietary and not really meant for reading other than my Quicken, probably for a reason as it is messy.  
I would recommend finding a way to export the qdf into an OFX (Open Financial Exchange) or qif file.  I have done some financial and quickbooks automation and I did something similar.  The problem is if you don't export to an exchange format, each version differs and strange things happen for many conditions that since they aren't documented (QDF) it becomes a bad situation for the programmer.
OFX is what allows online banking, brokerages and apps like mint.com securely get financial data.  It is a standard and consistent.  Finding a way to this is much better if at all possible.
Reading quicken data files