Access to hardware and mechanical design in addition to software
Complete Hardware Design including schematics, BOMs, gerber such that a production lot can be started immediately
Access to mechanical design to enable fine-grained customization of not just the internal electronics but also the associated housing
Software deliverables including the toolchains (complilers etc), packaging (yocto) mechanism to build your own linux distributions, and all components included in "developer license".
Flexibility to not just customize hardware but also extend software and add new functions / applications as may suit your application needs