Regarding this rather gray topic, I asked Google Gemini to conduct a deep investigation, and I feel it is quite a valuable reference.
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1. Introduction: The Misconception of "Openness" in Aeronautical Information and the Legal Reality
1.1 Raising the Issue
With the acceleration of digitalization, many countries worldwide have made their Aeronautical Information Publications (AIP) freely available via the internet. This status quo has created a widespread illusion among users that "aeronautical information is a public product with no copyright restrictions." However, as evidenced by your concern regarding the question "How exactly does eAIP copyright work?", the actual legal situation is extremely complex. "Gratis" (free of charge) and "Libre" (freedom to use) are two legally distinct concepts, a distinction particularly pronounced in the field of aviation data.

This report aims to clarify the global legal landscape regarding eAIP copyright, redistribution rights, and commercial use by analyzing ICAO regulations, the domestic laws of major countries (US, Europe, China, Oceania), and the customs of the commercial data market.

1.2 Evolution of Rights in Aeronautical Information Management (AIM)
ICAO Annex 15 stipulates the obligation of states to guarantee the "quality" and "timeliness" of aeronautical information, but this does not imply a requirement for states to waive copyright. On the contrary, to ensure data accuracy and prevent erroneous data from circulating and causing aviation accidents, many countries strictly control data dissemination channels through copyright laws or disclaimer clauses. Therefore, the so-called "openness" of "most countries" usually refers only to accessibility, not the openness of rights.

2. International Legal Framework and the Principle of National Sovereignty
2.1 The Chicago Convention and Data Sovereignty
According to the 1944 Convention on International Civil Aviation (Chicago Convention), states possess complete sovereignty over their national airspace.
The airspace classification, restricted areas, and route structure contained in the AIP are not merely technical data; they are a legal expression of national sovereignty in three-dimensional space.
Therefore, claims to rights over AIP data are often viewed as an extension of national "airspace sovereignty" in the digital realm.

2.2 ICAO's Cost Recovery Principle
ICAO itself maintains strict copyright over its publications.
More importantly, ICAO Doc 9082 "Policies on Charges for Airports and Air Navigation Services" explicitly states:
Cost Recovery: ICAO allows states to recover the costs of providing Air Navigation Services (ANS) from users.
Legitimacy of Data Sales: Selling AIPs, charts, or charging data licensing fees to commercial data providers (such as Jeppesen) is considered a legitimate means of recovering the maintenance costs of the Aeronautical Information Management (AIM) system.
This principle serves as the legal and economic basis for Europe, Australia, and other regions to exercise copyright over AIPs and impose commercial fees.

3. The Public Domain Exception: The US Model
The United States is one of the very few countries globally that truly achieves "complete openness" regarding data, which has led to a misjudgment by users regarding the openness of global data.
3.1 Legal Basis: No Copyright for Federal Government Works
According to US Copyright Law (17 U.S.C. § 105), works created by federal government employees within the scope of their employment are not subject to copyright protection.
Complete Public Domain: Digital products such as AIPs, Sectional Charts, and Terminal Procedure Charts produced by the FAA belong to the public domain.
Free Use: Anyone can download, copy, modify, and commercially sell them for free.
Giants like ForeFlight and Garmin Pilot have built vast commercial empires based on this free official data.

3.2 Liability and Disclaimers
Although there is no copyright, the FAA assumes no liability for third-party processed data and requires third parties to remove official FAA markings when using its data to avoid creating the misconception of official endorsement.

4. The European Model: Strict Copyright Management and Database Rights
In stark contrast to the US, European countries view aeronautical information as "high-value intellectual property."
Here, "open" only means "publicly accessible," and absolutely does not mean "freely usable."

4.1 Legal Structure of the European Aeronautical Database (EAD)
The European Organisation for the Safety of Air Navigation (Eurocontrol) operates the centralized European Aeronautical Database (EAD).
Ownership: Data within the EAD is owned by Eurocontrol or the individual data-providing states.
The user agreement for EAD Basic (free version) explicitly prohibits commercial utilization, systematic scraping, and redistribution of data.
Non-Operational Use: The freely available public data is intended for "non-operational purposes" or demonstration only; its use for actual flight navigation is strictly prohibited.

4.2 United Kingdom (NATS): Crown Copyright
The UK's Aeronautical Information Service is provided by NATS, and its data is protected by "Crown Copyright" or NATS' own copyright.
Copyright Notice: The UK AIP explicitly states "© Copyright NATS Limited," prohibiting copying, storing, or redistribution without written permission.
Authorized Sources: The UK Civil Aviation Authority (CAA) defines an "Authorized Source" regime for aeronautical data via document CAP 1054; third-party data distribution without authorization is deemed non-compliant.

5. The China Model: Barriers of National Security and Mapping Laws
Regarding the Chinese eAIP, which is of most concern to you, the legal environment is the most unique globally.
Here, "copyright" issues often take a back seat to "national security" and "mapping compliance" issues.

5.1 The Red Line of the Surveying and Mapping Law
In China, aeronautical charts and coordinate data are regarded as "surveying and mapping achievements."
Geographic Information Security: According to the "Surveying and Mapping Law of the People's Republic of China" and relevant regulations, high-precision geographic information involving military facilities and important target coordinates constitutes a state secret or controlled data.
Provision Restrictions: It is illegal to provide unpublicized surveying and mapping results to foreign organizations or individuals without approval from the administrative department of surveying and mapping under the State Council.
This directly cuts off the path for foreign commercial companies (such as Navigraph/Jeppesen) to legally obtain high-precision data for all of China.
Qualification Barriers: Engaging in the production of aeronautical charts requires "navigation electronic map production qualifications," which are extremely difficult for foreign enterprises to obtain.

5.2 Rules for Civil Aeronautical Information Work (CCAR-175TM)
The Civil Aviation Administration of China (CAAC) has strict regulations regarding the issuance of aeronautical information.
Issuance Monopoly: Only the CAAC and its authorized bodies (such as the Air Traffic Management Bureau Information Center) have the authority to issue valid aeronautical information.
Third-party unauthorized issuance or tampering with official data is a violation.
User Agreements: Official Chinese aeronautical information platforms (such as the "General Aviation Information Platform") explicitly prohibit acts that infringe copyright protection measures and data usage behaviors that endanger national security in their user agreements.

5.3 Practical Impact
Therefore, although Chinese AIP data can be partially viewed online (requiring real-name registration), it is by no means "open data."
Any unauthorized bulk downloading and packaging for sale (such as the Yinlei.org model) exists in an extremely high-risk legal gray area, and may even violate criminal law.

6. The Mixed Model in the Asia-Pacific Region
6.1 Australia (Airservices): Restricted Creative Commons
Airservices Australia adopts a model that appears open but is actually restricted.
Copyright Terms: Its AIP is protected by copyright. Although personal non-commercial use is permitted, it explicitly excludes "internal business purposes."
Redistribution Prohibited: Redistribution, storage, or the establishment of mirror sites is strictly prohibited without written permission.

6.2 New Zealand (CAA NZ): Truly Open Data
New Zealand is the most open example in the region and even the world, alongside the United States.
CC BY License: The AIP and charts of the New Zealand Civil Aviation Authority mostly adopt the "Creative Commons Attribution (CC BY)" license agreement.
Open Crown Copyright: Although Crown Copyright is retained, as long as attribution is provided, commercial entities are free to copy, distribute, and adapt.

7. The Commercial Logic of "Gray Areas" in Flight Simulation
The misconception that "global AIPs are public" largely stems from the "grab-and-go" habits of the flight simulation community.
7.1 The Data Chain of Navigraph and Jeppesen
Navigraph, well-known to flight simulation users, does not directly use national AIPs but purchases data licensing from Jeppesen.
Data Cleaning: Jeppesen obtains raw data (AIP) from official national sources and performs standardization processing.
This "processing" creates a new copyright.
Licensing Restrictions: Navigraph's license is strictly limited to "Simulation Only" (Game-based Learning) and is strictly prohibited for use in real flight, in exchange for lower licensing costs.

7.2 Risks of Community Redistribution
The PDF download services provided by personal sites like Yinlei.org essentially constitute "redistribution" of copyrighted data without authorization from official bodies (CAAC or other national AIS).
Official Stance: Most national AIS authorities adopt a "tacit approval" attitude towards such non-profit or micro-profit enthusiast behavior, but this does not mean the behavior is legal.
The China Exception: In China, due to the involvement of the "Counter-Espionage Law" and the "Data Security Law," the risk of such behavior is far higher than simple copyright infringement.

8. Conclusion: The Global Spectrum of AIP Copyright
"How exactly does eAIP copyright work?"
The answer depends on the country you are referring to.

Final Recommendation: Although you can "view" AIPs from various countries on the internet, the vast majority of countries (except the US and New Zealand) legally prohibit unauthorized scraping, packaging, and redistribution. For commercial plans, directly lifting official PDFs is unsustainable and high-risk. One must seek officially authorized data sources (such as Jeppesen/Lido) or conduct data production through compliant mapping qualifications.