Both of you are wrong, in one sense or another...
Helvetica was designed over 50 years ago by Linotype, which was acquired by Monotype several years ago. Adobe has nothing to do with licensing Helvetica. You can buy a license to use Helvetica from one of Monotype's resellers, which includes Adobe, or pick a reseller from Monotype's web site. Licenses for this font start at around $29 for one font, and families of Helvetica can run well over $1000. Buying a license doesn't mean you "own" a font - it belongs to the foundry that licenses it.
Apple has been licensing Helvetica (and the other original Mac "core" fonts) since 1990, around the time I used my first Mac in college, and the fonts installed with OS X. I favored Palatino, personally. I generally subscribe to a service, currently Adobe's Creative Cloud, that includes the licenses I need at the time.
You can't "port" or "copy" one of those fonts from one platform to another, it doesn't work that way, and it's not legal. You might be better off choosing a cross-platform font, or ponying up for the font(s) you want. Keep in mind that cross-platform fonts can render differently between platforms, but that's another story.