Whirlwind over Vietnam : made on IL-2's code or not?

[Warhound]

Well as above, was Whirlwind over Vietnam made using parts of Maddox games code for IL-2 , or did G5 write (all of) the code themselves?

I know this doesn't belong here perse...but figure it's the best place to get a correct and possibly even a moderaters answer.
Reason I ask is because a friend is convinced it was made on Il-2's code, while all I can find is that it was published by 1C in the USA but seems to be developped independently by 5G.

Anyone who can clear up this mystery for us?
Would be more tempted to try it out if it does (partly) use IL-2 code.