Unilateral promises themselves are not legally binding, and donations do not constitute a valid contract, as these lack consideration (or "causa," a related concept in civil law). It's also evident that intellectual property licenses should be considered contracts.

So, a license must be a valid contract that requires a mutual exchange of positive or negative promises.

While the most widely used permissive licenses (such as MIT or Apache 2.0) provide a valid consideration in terms of reputation and exposure because the original author information must be kept, some ultra-permissive licenses, such as Zero-Clause BSD do not provide such obligations from the licensee to the licensor (CC0 on the other hand provides a lengthy explanation on licensor's moral motivations, which probably constitutes a valid consideration).

However, there is a waiver of responsibility included, which is likely more of a disclaimer than a significant element of consideration.

It seems that in the case of Zero-Clause BSD, the licensor gets nothing from the licensee.

In this case, is there a valid, binding contract between the licensor and the licensee restricting the legal actions of the licensor?

  • Why would the licensor wish to take legal actions regarding something like this? The terms of the clause even preempt licensor's need to be a third-party plaintiff. Nov 11, 2023 at 14:16
  • @IñakiViggers If this is not a binding contract, the licensor might want to defend their copyright later for any reason (such as greed and money), placing the licensee into a trap where the licensee could be liable for a copyright infringement whenever the licensor chooses to practice their rights.
    – Solarius
    Nov 12, 2023 at 12:13
  • "placing the licensee into a trap". Licensor's revocation of waiver would have no effect on the licensee who already relied on the clause. Quite the contrary, the licensee could have a viable claim of promissory estoppel in that scenario. Nov 18, 2023 at 21:06

2 Answers 2


Probably not

There is no obligation placed on the recipient to do or refrain from doing anything, so it appears that there is no consideration flowing from the licensor to the licence.

A court might interpret the disclaimer as an obligation on the licensee not to sue but it isn’t phrased that way and, in any event, it would be an unenforceable term as there are some liabilities on a supplier that cannot be disclaimed by contract.

So, this licence is not a contract, it’s a gift. A gift-giver can be liable for flaws in the gift that they are aware of but not generally otherwise.



That is part of the license, and being free from and Lawsuit is valid consideration. The exchange here is "You get to use my software, I get to have no liabilities to you."

If that is a valid clause is to be tested in court.

  • 1
    "being free from and Lawsuit is valid consideration." Not really. Parties' allocation of risks falls short of consideration as understood in contract law. Nov 11, 2023 at 15:25

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