The main issue would be getting the required EMI/RFI emissions certifications, which will vary by location, and making sure you are not using any non-GPL software, of which the full Raspbian with Desktop has several pieces (like Oracle Java, for example). If you only need Raspbian Lite, you should be okay, but you need to look into this in detail to be sure. I don't think Raspbian Lite has any non-GPL software (other than the RPF firmware), but I'm not 100% sure.
Of course your other option would be to roll your own GNU/Linux, which would give you full control over what's in it. Or you could do your own custom machine level software, in which case you would own the license/trademark/copyright, etc.
And then there's the issue of which Raspberry Pi you want to use. If you are looking at using the Pi Zero, forget about it. This comes up all the time, and it's a dead end. The Compute Module is the Pi designed for commercial use, but the PiB+, 2B or 3B could likely be sourced in sufficient quantities as well.
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?