Windows – Possible to build an IPA file on Linux/Window

No - the IPA format does not make source code inclusion mandatory, so there’s no general way to do what you ask. As alluring as the idea is, just because something is possible on Android (What you’re talking about is not in the sense you want it), doesn’t mean it will be possible on iOS.

Now, if the developer decides to embed the source code into the IPA - you will be able to read it depending on the method of packaging it since the IPA contents are well documented by Apple on the developer site and many utilities exist to decode the application bundles.

The answer is almost YES!

I managed to install new builds of the same app on the devices via Fabric.io without apple dev subscription. (I guess you can also distribute them with iTunes. Send ipa to tester, and it should be able to install it via iTunes.)

The only disadvantage is that you have to connect the device to Xcode at least once. Then you can remotely install new versions. (I didn't find the way to do it manually knowing the udid)

When you connect the "unknown" device to xcode 7, there is a fix issue button in Target general settings. Fix the issue and Xcode will generate a new Provisioning profile with this device included. (you can find it in ~/Library/MobileDevice/Provisioning Profiles)

Than you can use this provisioning profile to distribute apps via Fabric.io

1. Signup on Fabric.io
2. Setup Fabric for your project (there is a step by step guide)
3. Make sure that xcode uses right prov. profile to sign it. Automatic worked for me.
4. Xcode>project>archive
5. fabric helper will detect the build and you will be able to distribute it.

Sorry guys who are not proficient enough with Xcode, I don't have much time to add less error prone guide, but I hope this answer will help somebody with ideas.

TIP: use this quicklook plugin to see inside ipas and prov. profiles!