Flexible Usage of GNU-Licensed Libraries in Open Source Projects

Introduction

The GNU General Public License (GPL) and the Lesser GNU General Public License (LGPL) are widely used open-source licenses. These licenses impose certain conditions on the distribution and modification of software. Understanding how to use these licenses in your projects is crucial for maintaining compliance with open-source principles. This article explores the implications of using a GNU-licensed library while disallowing its distribution, and provides guidance on alternative licensing strategies.

GNU Licenses Overview

To understand the limitations and possibilities, it is essential to have a solid grasp of GNU licenses. The two primary GNU licenses are the GPL and the LGPL. Each has its unique characteristics:

General Public License (GPL)

The GPL is a strict open-source license that requires all derived works to be open and freely distributable. Any software incorporating a GPL-licensed library must also be released under the GPL. This includes commercial and non-commercial use. Thus, attempting to disallow distribution in a GPL-licensed project is not feasible.

Lesser General Public License (LGPL)

The LGPL is more permissive and designed for use in libraries. It allows developers to use the library in proprietary software without releasing the modifications. However, if developers modify the library itself, those modifications must be released under the LGPL. Additionally, the LGPL does not restrict the distribution of the software that uses the library.

Key Points

The core of open-source licensing is the principle of free redistribution, modification, and use. Imposing any restrictions—whether commercial or non-commercial—contradicts these principles. Here are the key considerations:

Open Source Definition

Open source licenses are designed to promote collaboration and innovation. Imposing restrictions is generally not in line with the open-source ethos. Any attempts to restrict the distribution of open-source software may lead to legal and ethical conflicts.

Creating a New License

If you wish to create a module that uses a GNU library and restricts its distribution, creating a custom license could be an option. However, such licenses might not be recognized by the open-source community, and you could encounter significant legal challenges. It's important to consult with legal experts to ensure your custom license is both enforceable and aligned with open-source principles.

Conclusion

In summary, if you plan to use a GNU-licensed library in your project, the GPL requires your entire project to be open and freely distributable, including both commercial and non-commercial uses. If you need more control over distribution, exploring an LGPL library or developing a proprietary solution may be more appropriate. The key takeaway is that GNU licenses, especially the GPL, are not compatible with restricting distribution in any form.

LGPL Alternatives

If you choose to use an LGPL library, you can incorporate it into your proprietary or closed-source project without imposing any restrictions. However, if you make any modifications to the library itself, those changes must be shared under the LGPL. This provides a flexible solution for integrating open-source components into your project while maintaining control over your proprietary code.

Key Takeaways:

GPL requires all derivative works to be open-source and freely distributable. LGPL allows for more flexibility by permitting closed-source integration. Creating a custom license can be challenging and may not align with open-source principles. Exploring alternative libraries or developing your own solution offers more control over distribution.

References:

GNU GPL-3.0 GNU LGPL-3.0 Open-Source License Information