According to James Gunn the Skrulls are partially owned by Marvel and somehow the badoon are owned by Fox. I guess Marvel studios decided two major alien races and basically all the minor ones would be enough.
But the weird thing is that knowing they dont have rights to the badoon, they still made badoon concept art for guardians
But then they made similar concept art with Chitauri
EDIT: Later images are Sakaarans not Chitauri.
Edited by sunshineblotters - 5/29/15 at 7:25pm