Ewan, I believe you are mistaken. There have been numerous examples of vendors selling devices with, initially, a 'closed' kernel. E.g. TomTom. They all ended up with having to provide source, and a way to let the customer build&install a new kernel from that source. Today even embedded devices like Panasonic TVs follows this.

After reading up on 'tiviosation' on Wikipedia I still maintain the above. What I was replying to was the statement '..might allow them to make their own kernel with their branding, that the user cannot remove.'.