open source license
 

I often see that various devices (TV, settopbox) use open source, and they (have to) declare that fact clearly.
What about android/ios 'apps'?
Is there a way to see what FOSS libraries, etc.. were used in those, if any?

I forgot the details, but years ago somebody was able to prove that a router contained open-source software by analyzing its connection response. You may also be successful by looking for certain strings or bit patterns in files.
That requires special knowledge and skills.

Other than that, it’s impossible to find out if a software product is based on open-source, if the authors don’t disclose it.

Of course it's highly possible the open-source content is disclosed. On a screen about five mouse clicks down a menu tree and only visible when the moon is full!

And in Comic Sans font!

do they?
where? how?

android "apps" do not have to be open source afaik.
in any case, an apk file is just an archive that can be opened and examined.

android itself is open source, but contains binary blobs and other proprietary and/or closed source stuff.
this information is openly available: https://source.android.com/

thanks.
well, my old Panasonic plasma TV has GPL License somewhere in menu, also Sony TV, IIRC.

Sky satellite boxes, on my Q box hitting Menu - Settings - System Info - Software Disclaimer shows a list.

Also http://sky.com/opensourcesoftware/