Hello Manuel, you keep diverting and going around the main subject.
The subject aren't the tools using the TSX format, or whether they are opensource or not.
The subject is to support a format increasingly accepted by the community and preservation groups by openmsx, the reference emulator for many MSX people.
And I say that your argument is not the main subject because openmsx incorporates many extensions that are not open source at all ... and there they are.
It is a problem of will, of will to do it (or not).
Anyway, as we said in a past post, there are public TZX2WAV sources (although without 4B support) and in the next few days there will be a PHP opensource converter for the Linux people that don't like wine 
What will be the next issue, Manuel?
wav.php
...and...
tsx2wav.php
Not problem 
But this is not a replacement for an hypothetical TSX support from openMSX team.
TSX support can give much more added value to the emulator execution as a simple WAV.
TZXDuino sounds very Spectrum. Better a TSXDuino that you can insert in your MSX slot 