I have successfully tested the Bitvise SSH server, which runs natively on Windows.  It's not open source, but the licensing fee is quite reasonable at $99.  The only issue for us is that it doesn't integrate with Caché.  The user needs to have a separate local or domain Windows account to SSH in to the server prior to logging in to Caché.  The integrated telnet service that's included as part of the Caché installation doesn't require users to keep a separate Windows account.

Okay.  I'll take a look at both of these ideas, i.e. Single Sign On with Active Directory/Kerberos or moving Caché to Linux.

Thanks Dmitry!  This helped, although this solution still has some concerns for my organization.  In particular, it means that the Caché user will need a local account on the server in order to log in to the server, via secure shell, before logging in to Caché.  This would, unfortunately, open another security concern with my organization.  The end user would also be burdened with the hassle of using a separate Windows account for this purpose.  It's a shame that Caché on Windows doesn't support an integrated SSH server, as it does for telnet.