Source code availability is not an issue, because it is part of the certification process to provide it.
The problem is having the money to pay for a certification, which becomes invalid the moment anything gets changed, namely compiler being used, source code, or if any of the third party dependencies gets updated.
Actually they already authorize stuff like Qt.
Computer systems where human lives are put in risk belong to what is called High Integrity Computing.
There are very strict coding standards, where even C looks more like Ada than proper C.
https://ldra.com/medical/
https://www.qt.io/qt-in-medical/
https://www.vectorcast.com/testing-solutions/software-testin...
Source code availability is not an issue, because it is part of the certification process to provide it.
The problem is having the money to pay for a certification, which becomes invalid the moment anything gets changed, namely compiler being used, source code, or if any of the third party dependencies gets updated.