It makes perfect sense to me that paying $99/year for the App Store is cheaper than $0.50/install. But you shouldn't have to pay anything to install Free Software in the first place, so I can also see why some people would consider protesting Apple's policy to be invaluable.
And frankly, most of the iOS ports of FOSS aren't themselves are closed source, so they don't really count as FOSS, but if the people who, say, ported OpenOffice to iPhone gave it to the Apache foundation? I can't see why they wouldn't release it.
I thought the restrictions/Apple's fee around those were different?
e.x. You average $2 per install on in-app purchases you get $1.40 (30% Apple fees) on app store or $1.50 ($0.50 install fee) on 3rd party store
AltStore or Epic complying with Apple's current dubious terms makes no real difference.