Different components of Poky are under different licenses (a mix of 
MIT and GPLv2). Please see:

bitbake/COPYING (GPLv2)
meta/COPYING.MIT (MIT)
meta-extras/COPYING.MIT (MIT)

which cover the components in those subdirectories. This means all 
metadata is MIT licensed unless otherwise stated. Source code included 
in tree for individual recipes is under the LICENSE stated in the .bb 
file for those software projects unless otherwise stated.

License information for any other files is either explicitly stated 
or defaults to GPL version 2.