Not really - if they provide an SDK it is to make your job easier. While you could program for most things without the SDK, it would be a lot more trouble than it is worth, as you would have to duplicate all the clever software that the SDK encompasses. The chances are that the device is fairly dumb - just a tiny scanner - and all the clever fingerprint matching stuff is done by routines in the SDK. Tall to the manufacturers - they will quite probably provide it.
[edit]They do: and it's free.
http://www.secugen.com/download/sdkrequest.htm[
^][/edit]