Do I understand well, MLP-compressed DVD can not be
free on Linux, because of MLP algorithm is patented?
There may well patents on the technology, but that doesn't mean that a
libre software decoder is impossible, just more difficult. I think
patents on some parts of MLP were applied for, but I don't know if
they were granted yet. Patents within standards can be licenced on a
royalty-free basis - it's at the discretion of the patent holder, as
I understand it.
Meridian is mostly a hardware company, but they do sell MLP software
encoders for Windows, so there is the potential for competition from
a libre software tool. However, Meridian may be interested in seeing
their format adopted as widely as possible, especially since DVD-A is
not yet a mainstream format.
I suggest you read up on MLP using these white papers by Bob Stuart,
if you haven't already:
then make an enquiry to Meridian about Linux encoder/player support,
open standards etc etc. I'd be very interested to hear the response,
and I'm sure others would be too.