Forbid LLM contributions (#242)

CONTRIBUTING.md

@@ -1,7 +1,14 @@
 Want to contribute? Great! First, read this page (including the small print at
 the end).
 
-### Before you contribute
+* [Before You Contribute](#before-you-contribute)
+  * [Code Reviews](#code-reviews)
+  * [File Headers](#file-headers)
+  * [The Small Print](#the-small-print)
+* [Large Language Models](#large-language-models)
+
+## Before You Contribute
+
 Before we can use your code, you must sign the
 [Google Individual Contributor License Agreement](https://cla.developers.google.com/about/google-individual)
 (CLA), which you can do online. The CLA is necessary mainly because you own the
@@ -17,10 +24,12 @@ us first through the issue tracker with your idea so that we can help out and
 possibly guide you. Coordinating up front makes it much easier to avoid
 frustration later on.
 
-### Code reviews
+### Code Reviews
+
 All submissions, including submissions by project members, require review.
 
-### File headers
+### File Headers
+
 All files in the project must start with the following header.
 
     // Copyright 2019 Google LLC
@@ -29,7 +38,21 @@ All files in the project must start with the following header.
     // license that can be found in the LICENSE file or at
     // https://opensource.org/licenses/MIT.
 
-### The small print
+### The Small Print
+
 Contributions made by corporations are covered by a different agreement than the
 one above, the
 [Software Grant and Corporate Contributor License Agreement](https://developers.google.com/open-source/cla/corporate).
+
+## Large Language Models
+
+Do not submit any code or prose written or modified by large language models or
+"artificial intelligence" such as GitHub Copilot or ChatGPT to this project.
+These tools produce code that looks plausible, which means that not only is it
+likely to contain bugs those bugs are likely to be difficult to notice on
+review. In addition, because these models were trained indiscriminately and
+non-consensually on open-source code with a variety of licenses, it's not
+obvious that we have the moral or legal right to redistribute code they
+generate.
+
+