IFTAS on Nostr: you will not be able to modify someone else's app and use it without your ...

you will not be able to modify someone else's app and use it without your modifications also being certified.

That would for obvious reasons render the app useless.

The spec is open, the pathway to implementation is open.

If you download app X to use as a consumer, you cannot modify it. Well, you can, but it won't work. That's the point. It immediately becomes non-compliant. Go build a compliant one and use that.