Metal Slug 4 question

Sorry if this question has been answered in the past.....

Mega Enterprise (Korean company) programmed Metal Slug 4 if I remember correctly. But the end credit is showing all the Japanese SNK/Playmore staff were involved in production.....well????

So it's SNK/Playmore programmed/published this game or Korean team?

if you read the line above is says "special thanks to"

They based their work off of pre-existing code and graphics made by the original metal slug teams. That doesn't necessarily mean that they were involved...