Many SFTP server and software (including WinSCP) use the initial "welcome message" to make decisions based on the version of software used by the other side of the connection. The welcome message is a string prefixed with "SSH-2.0-" that usually includes the software's version number. In case of Rebex SFTP, this string is "SSH-2.0-RebexSSH_{version}".
We don't know whether Windriver can be configured to behave differently based on different strings, although we know that our SFTP server can (the string is accessible from Authentication
event arguments).
However, making business decisions based on this is quite problematic because the welcome message can easily be spoofed or even modified along the way (they are transmitted before a secure channel is established).
A slightly better alternative to this would the vendor-id SFTP extension which is part of the SFTP protocol and is only sent over a secure channel after the user has been authenticated and an SFTP session has been established. Even though we don't support this yet, we can easily add it on demand. However, even this could be easily spoofed in other clients.
A better approach would be to have each client generate a unique private key on installation, send the corresponding public key to a server and use keybased authentication to. However, this is complicated and still far from being hacker-proof.