Btrieve legacy migration

Hello,

I am writing an application in C# that I am trying to integrate with a
legacy program that stores its information in Btrieve databases.  I am
looking for information on how to do this.

Due to financial constraints, as well as licensing problems,
purchasing a copy of Progressive Server is not very feasible.
Basically, my program needs to be able to read the information stored
in this database without installing Progressive.

I am basically looking for one of two things: an open-source library
for reading btrieve data files, or a description of the file format.

I have been able to find many descriptions of file.ddf and field.ddf,
but the program I am integrating with only seems to use an index.ddf.
Any of the freeware programs I have found require a file.ddf and
field.ddf file to work.

There have been some hints that the SQL reference manual from the
Progressive website might have the file format I'm looking for, but I
have not been able to find any details.

This is all further complicated by the fact that I have no idea what
version of the file format I am working with, but I suspect it to be
pre-6.15.

If anyone could point me towards some solutions to any of these
problems, I would really appreciate it.  I have been banging my head
against a wall all week.  Thanks.

-Daniel