The reason you get this message is since when I was implementing SFTP protocol I was using version 3 and this is the only version currently supported.
However here are the changes from protocol 2 to 3:
o The SSH_FXP_READLINK and SSH_FXP_SYMLINK messages were added.
o The SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY messages were
o The SSH_FXP_STATUS message was changed to include fields `error
message' and `language tag'.
So you can basically make a change to work with 2.0 version too.
You will need not to use link operations, it seems.
And make some modification to the SSH_FXP_STATUS message so in case of version 2.0 it will simply ignore those new 2 fields that were added.
Unfortunately I don't have access to SFTP version 2.0 which is the main reason I didn't implement it.
If you make a changes that it will work with version 2 and 3 and want me to include it in the source, feel free to let me know.
Hope it helps.