Isn't Neat Image free ? It's called demo version, but it is stated on
their site that you can use it for free as long as you want for
non-commercial purposes

When I bought NI a couple of years ago there were four or five
versions, I *think* the free one only worked on jpegs, not on tiffs, so
it's not much use for many of us. IIRC there was a cheap version for 8
bit tiffs, a more expensive version for 16 bit/channel files, and
another more expensive version that was a Photoshop plug-in (instead of
standalone). Something like that ...

Bill