I can find no information about what limit they’re claiming. You can use a maximum of 5 different Apple ID simultaneously on a device but that’s pretty obscure.
it is 5 devices that you can use personally with an Apple ID (so, you as a single person can own 5 devices that can receive things you've paid for on the app store, like music and programs.).
It has subsequently been increased to 10.
https://www.google.com/search?q=Apple+Developer+Agreement+5+...
TIL it's now 10 devices...
Why would that ever be a consideration?
Distribution restrictions on top of GPL and they don't own the copyright on all the code without a CLA which prevents licensing under something other than GPL for the App Store.
iPad, iPod, iPhone, MBP, iMac, AppleWatch, ... oh, that's already six devices tied to the same account.
I think the idea is that you don't tie all your friends' devices to your account to share apps etc., but I am just guessing.
I believe the GP was just posting the text from Pidgine website, not writing it.
Quick search reveals that up to 5 devices can be tied to the same Apple account: https://discussions.apple.com/thread/8030144
Sorry, but I'm not familiar with this – could you share more please?