Installer.app and pkg

Hello,

The document expected for the app Installer (see 
gap/system-apps/Installer) is 'pkg'.
I found this documentation:

Flat Package Format - The missing documentation
http://s.sudre.free.fr/Stuff/Ivanhoe/FLAT.html

So I have two questions:

1) Is this 'pkg' format intended to be used only on MacOS? Or could we 
try to implement it with GNUstep?

2) If the answer is yes, could we envisage to provide universal 
packages (I mean bundles with all the needed binaries for arm64, 
amd64...) thanks to such a way to install GNUstep apps?

Regards,
Patrick

-- 
Patrick Cardona - Pi400 - GNU/Linux aarch64 (Debian 13.2)
Xorg (1:7.7+24) - libcairo2 (1.18.4-1+rpt1 arm64)
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- MUA: GNUMail (1.4.0)