What ssh libs does Chilkat use?
It looks to me as The software mimics Putty, and Putty is not the real Library.
AFAIK it is a proprietary implementation. It does mimic Putty in the client identifier as stated in the documentation for the ClientIdentifier property:
The client-identifier string to be used when connecting to an SSH/SFTP server. Defaults to "SSH-2.0-PuTTY_Release_0.63". (This string is used to mimic PuTTY because some servers are known to disconnect from clients with unknown client identifiers.)