I don't think you can use a softphone with the lite version.

There really isn't any good options on the 200ICP for softphone without getting full blown YA.

I think it might be possible to use a Multitech fxo sip converter (MP130) tied to an analog port in conjunction with a freeware sip softphone like Counterpath's X-lite. You could then setup phone twinning to keep one number access.

This scenario is hypothetical, since I haven't ever tried it.