Also many hardware vendors use their stack to differentiate themselves from other competitors as at the end they tend to 'do' the same things. That stack keeps at bay people just copying their design wholesale and then undercutting their margin and using their drivers. Then even if they are willing, they many times included some lib they bought from someone else. They may even have the full code to use and have changed it as needed. But that 3rd party is usually some consulting group and guess what one of the very few things they sell is. It is a huge mess.