Bubba Kush started in '92 (from some random amazing bagseed that was deemed "Kush" - due to its bud structure). In '94, he received some Northern Lights from California. After careful selection, he found his keeper pheno (which was named "Bubba"). Somewhere around '96, in Los Angeles, his "Kush" hermaphrodited. When it did, it pollinated the "Bubba" (Northern Lights) strain, and hence, created Bubba Kush.
So as to the genetics, they are Northern Lights x Kush. GreenHouseSeedCompany does not follow the original genetics, instead, theirs is:
("Bubblegum" : Big Skunk x NL#5) x Kush
Also, there is no Kush in OG Kush. It was a phenotype of Chemdawg '91 that was Selfed. If my memory serves correct, Swerve brought it to Tahoe around '96.