In general, stay away from all kind of "Win..." stuff.
They win, you lose.
A sad story it is, but there are a few of these supported under Linux, so you may or may not be able to get them to work:
Your particular Losemodem must be supported.
You must be able to port the driver to SCO.
Search on 'Linmodem' - that should get you going ... but I would asess your chances as about 1-5% ...