The situation is a bit different from uTorrent Portable, that is a launcher package that download a freeware app during installation and without that app it doesn't work at all.
I think at the moment we can classify ArcThemALL! as Open Source with freeware components and in next release I'll create a plugin system to support external freeware apps like MPRESS (and eventually others), to keep the official package fully open source but at the same time to allow users to extend it with other compressors.
This could be a good solution, I think.. thanks for the report John and sorry for my error..
If there are freeware components of an app proper, then it is freeware with open source components. Open source means open source... as in fully open source. If in the main description of the app you're mentioning capabilities of a closed source component, then the app itself should be considered freeware. But you're promoting the fact that MPRESS is a feature when MPRESS is a closed source component with licensing issues around redistribution of EXEs and DLLs compressed with it.
In order to be open source, the description of the app proper shouldn't have anything to do with MPRESS, realistically. Perhaps a single line separated from the main description saying it can be added. And a warning when adding MPRESS within the app itself detailing that MPRESS is closed source and GPL and LGPL licensed binaries compressed with MPRESS may not be redistributed.
Like I said, having it both ways is disingenuous. Either it's an open source app and you promote its open source features and functionality and then, perhaps, mention that you can add some optional closed source bits. Or it's a freeware app with mostly open source components and you promote the closed and open source features and functionality. One or the other seems more honest.