I'm pretty sure that he would have shared the name of the wallet within the opening post if he really wanted to, but since he didn't do that, he probably didn't want to disclose that information publicly for any reason that he might have. Also, I didn't understand your reference about checking the license of the software to know if it's open-source or not.
What's the point of disclosing that information? Am I in danger if I publicly state that I use Bitcoin Core or Electrum? That makes no sense.
If software comes with General Public License or MIT license, for example, this means that the software is open-source.
Sometimes, under download sectino, website put the Github code of their open-source code. Easy way to check whether a program is open-source or not, is to check their license. Another method is to just google: Is [programname] open source? If answer is yes, then look for their source code. By the way, if you don't trust their executable file and only want to run what you see, then learn how to run from source. Electrum, for example, comes with a tutorial.
By the way, name the wallet you want to know if that's open-source or not, we will help.
I also don't think that one needs to first Google if a wallet or any program or project is open-source or not, all they need to check is their website and to try and find their repository which contains the source code. If one understands a bit of coding and can identify if they have their source code open to the public, they can identify whether the project is open-source or not.
I have never said that one needs to first Google if wallet is an open-source or not. First step, according to my quote, is to check it software's website if they include GitHub url.