LGPL 2.1 vs. LGPLv3

Attribute	LGPL 2.1	LGPLv3
License Version	2.1	3
Compatibility with GPL	Yes	Yes
Patent Grant	No	Yes
Additional Permissions	No	Yes
Compatibility with Apache License 2.0	Yes	Yes

Introduction

The GNU Lesser General Public License (LGPL) is a widely used open-source software license that allows developers to use, modify, and distribute software while ensuring that the source code remains open and accessible. There are several versions of the LGPL, with LGPL 2.1 and LGPLv3 being two of the most commonly used versions. In this article, we will compare the attributes of LGPL 2.1 and LGPLv3 to help developers understand the differences between the two licenses.

License Scope

LGPL 2.1 is a permissive license that allows developers to link their software with libraries licensed under the LGPL without requiring the software itself to be open source. This means that developers can use LGPL-licensed libraries in their proprietary software without having to release the source code of their own software. On the other hand, LGPLv3 includes additional provisions that require any software that links to an LGPLv3 library to also be open source and licensed under the LGPLv3 or a compatible license.

Compatibility

One of the key differences between LGPL 2.1 and LGPLv3 is their compatibility with other open-source licenses. LGPL 2.1 is compatible with a wide range of licenses, including the GPL, allowing developers to combine code from different projects with minimal restrictions. In contrast, LGPLv3 is more restrictive in terms of compatibility, as it requires any software that links to an LGPLv3 library to be licensed under the LGPLv3 or a compatible license. This can limit the ability of developers to combine code from projects with different licenses.

Patent Protection

LGPLv3 includes provisions that offer greater protection against patent litigation compared to LGPL 2.1. The patent clause in LGPLv3 ensures that users of the software are granted a license to any patents held by the copyright holder, preventing the copyright holder from asserting their patents against users of the software. This can provide greater peace of mind to developers who want to use LGPLv3-licensed software in their projects.

Digital Rights Management

Another area where LGPL 2.1 and LGPLv3 differ is in their treatment of digital rights management (DRM) technologies. LGPL 2.1 allows developers to use DRM technologies in their software, while LGPLv3 includes provisions that restrict the use of DRM. This means that developers who want to use DRM in their software may prefer LGPL 2.1, while those who are opposed to DRM may prefer LGPLv3.

Upgradability

One advantage of LGPLv3 over LGPL 2.1 is its upgradability. Since LGPLv3 includes provisions that require any software that links to an LGPLv3 library to be licensed under the LGPLv3 or a compatible license, developers can easily upgrade their projects to LGPLv3 without having to worry about compatibility issues. This can make it easier for developers to stay up to date with the latest version of the LGPL and take advantage of any new features or improvements.

Community Adoption

Both LGPL 2.1 and LGPLv3 have been widely adopted by the open-source community, with many projects choosing to use one of these licenses to ensure that their software remains open and accessible. However, LGPL 2.1 is still more commonly used than LGPLv3, as some developers may prefer the permissive nature of LGPL 2.1 over the more restrictive provisions of LGPLv3. Ultimately, the choice between LGPL 2.1 and LGPLv3 will depend on the specific needs and preferences of each individual developer or project.