3rd Party Libs in Samples (#4408)

Adding guidance on the proper usage of 3rd Party Libraries in our samples.

CONTRIBUTING.md

@@ -257,3 +257,23 @@ If the coverage data has been previously generated (for example, if you manually
 ### Visual Studio 2019
 
 You can also build the project by simply opening the repo directory in Visual Studio. Visual Studio will detect the `CMake` file and will configure itself to generate, build and run tests.
+
+## Samples
+
+### Third-party dependencies
+
+Third party libraries should only be included in samples when necessary to demonstrate usage of an Azure SDK package; they should not be suggested or endorsed as alternatives to the Azure SDK.
+
+When code samples take dependencies, readers should be able to use the material without significant license burden or research on terms. This goal requires restricting dependencies to certain types of open source or commercial licenses.
+
+Samples may take the following categories of dependencies:
+
+- **Open-source** : Open source offerings that use an [Open Source Initiative (OSI) approved license](https://opensource.org/licenses). Any component whose license isn't OSI-approved is considered a commercial offering. Prefer OSS projects that are members of any of the [OSS foundations that Microsoft is part of](https://opensource.microsoft.com/ecosystem/). Prefer permissive licenses for libraries, like [MIT](https://opensource.org/licenses/MIT) and [Apache 2](https://opensource.org/licenses/Apache-2.0). Copy-left licenses like [GPL](https://opensource.org/licenses/gpl-license) are acceptable for tools, and OSs. [Kubernetes](https://github.com/kubernetes/kubernetes), [Linux](https://github.com/torvalds/linux), and [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) are examples of this license type. Links to open source components should be to where the source is hosted, including any applicable license, such as a GitHub repository (or similar).
+
+- **Commercial**: Commercial offerings that enable readers to learn from our content without unnecessary extra costs. Typically, the offering has some form of a community edition, or a free trial sufficient for its use in content. A commercial license may be a form of dual-license, or tiered license. Links to commercial components should be to the commercial site for the software, even if the source software is hosted publicly on GitHub (or similar).
+
+- **Dual licensed**: Commercial offerings that enable readers to choose either license based on their needs. For example, if the offering has an OSS and commercial license, readers can  choose between them. [MySql](https://github.com/mysql/mysql-server) is an example of this license type.
+
+- **Tiered licensed**: Offerings that enable readers to use the license tier that corresponds to their characteristics. For example, tiers may be available for students, hobbyists, or companies with defined revenue  thresholds. For offerings with tiered licenses, strive to limit our use in tutorials to the features available in the lowest tier. This policy enables the widest audience for the article. [Docker](https://www.docker.com/), [IdentityServer](https://duendesoftware.com/products/identityserver), [ImageSharp](https://sixlabors.com/products/imagesharp/), and [Visual Studio](https://visualstudio.com) are examples of this license type.
+
+In general, we prefer taking dependencies on licensed components in the order of the listed categories. In cases where the category may not be well known, we'll document the category so that readers understand the choice that they're making by using that dependency.