Liability: self-built from open source or a purchased platform?

What is the difference in one sentence?

If you build it yourself, you are your own manufacturer; with a purchased platform, you have one. Almost everything else follows from this: who answers for defects, who closes security vulnerabilities and who is liable towards injured persons.

Question	Self-built from open source	Purchased platform
Warranty for the software	usually excluded (licence)	under the contract and the law
Who fixes defects and vulnerabilities?	your IT or a contracted service provider	the provider, under the contract
Product liability (from 9.12.2026)	possibly you, as manufacturer	the provider, as manufacturer
Obligations as a provider under the AI Act	possibly you	the provider of the platform
Proof (ISO 27001, DPA, SBOM)	you produce it yourself	supplied by the provider, where available
Dependence on the provider	none	yes, check the provision for insolvency

Who is liable for open-source software?

Hardly the rights holders. Common licences such as Apache 2.0 or MIT provide the software “as is” and exclude warranty and liability as far as the law allows. In Germany, making software available free of charge is often treated like a gift: the giver is then liable only for intent and gross negligence (§ 521 BGB, German Civil Code) and for defects only if they were fraudulently concealed (§ 524 BGB).

Anyone who builds an AI environment from such components therefore takes on the risk themselves: for defects, for security vulnerabilities and for whether the parts together do what they should. If you commission a service provider, they are liable under the contract you conclude with them, usually a contract for work or a service contract.

What does the new Product Liability Directive change?

Directive (EU) 2024/2853 replaces the Product Liability Directive of 1985. The most important points for AI:

• Software is a product (Art. 4(1)), whether it is installed or provided as a service. This covers AI systems too.
• Open-source exemption: Free and open-source software that is developed or supplied outside the course of a commercial activity is not covered (Art. 2(2)). If a company builds it into a product in the course of its commercial activity, it is liable as manufacturer.
• Own use: A manufacturer is also anyone who develops a product for their own use (Art. 4(10)(c)). What counts is the first use in the course of a commercial activity (Art. 4(9)). Whether and when this applies to a hospital or public authority that assembles an AI environment itself has not yet been settled by the courts.
• Substantial modification: Anyone who substantially modifies a product outside the manufacturer’s control and makes it available counts as manufacturer themselves (Art. 8(2)).
• Updates: The manufacturer is also liable for defects caused by updates or missing security updates, as long as it has control over them (Art. 11(2)).
• Easier burden of proof: Courts can presume the defect and the causal link, for example if the manufacturer does not disclose evidence or proof is excessively difficult (Art. 10).
• Who receives compensation: only natural persons, such as patients, citizens or staff (Art. 5). Property and data used exclusively for professional purposes are excluded (Art. 6).
• No contractual exclusion towards injured persons (Art. 15).

The Directive applies to products placed on the market or put into service after 9 December 2026. Germany is transposing it with a revised Product Liability Act (Produkthaftungsgesetz); the Bundestag passed it on 8 October 2026. There is no separate EU liability directive for AI: the Commission withdrew the proposal in 2025.

Who is a provider under the AI Act?

The AI Act distinguishes between providers and deployers. A provider is anyone who develops an AI system or has it developed and places it on the market or puts it into service under its own name, whether for payment or free of charge (Art. 3(3)). Anyone who builds an AI environment themselves and uses it in their own organisation can therefore be provider and deployer at the same time. For general tasks such as drafting texts or searching documents, the provider obligations are manageable; for high-risk applications they are extensive. More on this in the guide Own AI apps: when are you a provider under the AI Act?

The Cyber Resilience Act is similar: it applies to products made available on the market. For organisations that look after open-source projects (“open-source stewards”), it sets out separate, lighter obligations (Art. 24).

What should you check when buying?

• Warranty: What counts as a defect, and how quickly is it fixed? For rented software, German tenancy law applies; the rent is reduced in the event of defects (§ 536 BGB), unless the contract provides otherwise.
• Liability: Are there caps? For which damage?
• Updates and security vulnerabilities: How long does the provider deliver updates, and how do you report vulnerabilities to it?
• Proof: certificates, data processing agreement, list of software components (SBOM), penetration tests.
• Exit and insolvency: Can you get your data out? What happens to the software if the provider no longer exists?

How does this work with basebox?

basebox is a ready-made platform with a licence, support and updates. It builds on open-source components, such as vLLM for the AI model and Keycloak for sign-in; the full list is in the software bill of materials (SBOM), which customers see in their basebox and which you can receive on request before buying. basebox itself is not open source. If basebox becomes insolvent, the code is published as open source so that you can continue to run basebox; on the server, basebox runs on your hardware anyway. Proof such as ISO 27001, the data processing agreement and the status regarding the Cyber Resilience Act can be found under Security. You can continue to use existing hardware.

Not legal advice: This article gives an overview as of 11 October 2026. The new Product Liability Act had not yet been promulgated, and courts have not yet interpreted the new terms. Which liability applies in an individual case depends on your contracts. Have them reviewed by a lawyer.