Download can be found at the
Software Downloads Forum or
here.
Indeed no installation, just unpack in a chosen directory and run. But afterwards it appears to be in the registry yet.
Unfortunately, it doesn't use an INI file for the settings. Like color or enabling a stereo spectrum display.

It has the option to make a playlist, using the .MOL extension. When opening MPP again, it remembers the last one,
due to some registry key, still under the name of "Olivier Lapicque".

The ascii syntax of a .MOL file (using MOD files in the same directory) looks like this :
[DIRECTORIES]
\extmods2\wolfchild
[ARCHIVES]
[ARCHIVDIRECTORIES]
[FILES]
$ 01 - title1
$ 02 - title2
$ 03 - title3
etc
Quite simple to convert to other playlist formats I guess.
The ModPLug Player appears to have the same dialog as the ModPLug Tracker for actual sound-settings : The
Setup tab.
Where before or during playback e.g. panning can be widened, or a reverb added.
This Setup setting doesn't matter if one resaves a tracker-module.
But MPP has an option (as MPT does) to export the piece as a WAV file.

Here, the Setup defines the final output. Make a WAV file with Bass Expansion.
Starting with the possible variation on the Sound Card tab :

The Stereo Separation.
Then the Player tab. Bass expansion, reverb, and surround are the main variables.
The reverb has 29 presets. And surround will mean not only widening, but also short echoes between L-R.

Then there is the Equalizer tab, which has presets and saved custom settings.

This function can be switched on/off in other dialogs.
An option of MPP which MPT hasn't : it can open a WAV file as well to play.
Which means it can also save that file as another WAV file, including the
Setup.
So MPP could be a tool to quickly upgrade some soundfile with adding a reverb or so.
A simple
WAV editor in a sense.
EDIT: in the meantime I discovered another MPP option via R-click : Mixer Controls.

At least I found out that is has channel volume control plus speed and pitch.
I still have to investigate this. It also opens a new MPP dialog with a 'record' option.

I activated the record button but so far nothing specific happens.