Important Update: MegaMek License Changes Coming with Version 0.50.07

Hi everyone,

Today we have an important announcement about upcoming changes to how MegaMek is licensed. While this might sound like dry legal stuff (and let’s be honest, it kind of is), these changes will help ensure MegaMek continues to thrive as the fan project we all love.

Throughout this announcement, when we refer to “MegaMek,” we’re talking about the entire suite of programs: MegaMek (the tabletop simulator), MegaMekLab (the unit design tool), and MekHQ (the campaign management tool).

Why Are We Making This Change?

After 20 years of development, our project has grown into three interconnected programs, but they’ve been operating under different licenses. MegaMek and MegaMekLab use GPLv2, while MekHQ uses GPLv3. This inconsistency has created some technical challenges for our development team. Think of it like trying to share tools between workshops where each workshop has different rules about borrowing tools.

The current setup makes it harder for our developers to share improvements between programs, create common tools and libraries, and streamline our development process. Additionally, we’ve realized that using a software license for our creative content—such as artwork and unit data—isn’t ideal. There are better licenses designed specifically for this type of content.

By updating and aligning our licenses, we’re removing these barriers and setting ourselves up for more efficient development in the future.

What’s Changing?

Starting with version 0.50.07, we’re updating our licensing to create consistency across all three parts of our ecosystem. For reference, the current available version is 0.50.06, which remains under the existing licensing structure. Version 0.50.07 will be our next development release and the first under the new licensing model.

For the code itself, we’re upgrading MegaMek and MegaMekLab from GPLv2 to GPLv3, aligning them with MekHQ. GPLv3 is a widely-used open-source software license providing additional protections compared to GPLv2, including better patent protection and improved compatibility with modern development tools.

For our suite’s data and assets—things like unit files, artwork, and other non-code materials—we’re moving from GPLv2 to a Creative Commons license, specifically CC-BY-NC-SA-4.0. Creative Commons licenses are tailored specifically for creative content, making this a better fit for our non-code materials.

How Does This Affect You as a Player?

The short answer is that it doesn’t change how you use MegaMek at all.

The MegaMek suite remains completely free to download and play, just as it has been throughout our entire history. We know this is often the first question people have when they hear about license changes, so let’s be crystal clear: you will never have to pay to use any of the MegaMek suite. These license changes reinforce that commitment.

You can still create custom units and scenarios for personal use and share them with the community. Your saved games will continue to work, your campaigns will transfer normally, and any custom content you’ve created will remain compatible.

For Streamers and Content Creators

We know many of you share your MegaMek experiences through videos and streams, and we want to ensure you can continue doing so without concerns. Despite the non-commercial clause in the CC-BY-NC-SA-4.0 license, we explicitly grant permission for content creators to monetize videos and streams featuring MegaMek gameplay. This includes ads, donations, subscriptions, sponsorships, and platform partner programs.

The key distinction is simple: you’ll be monetizing your creative work about MegaMek (commentary, tutorials, entertainment), not our data itself. A Twitch stream using MegaMek or a YouTube channel about MegaMek tactics with ads is perfectly fine. A website hosting unit stats with ads or premium subscriptions based on our data files is not.

Monetized websites, apps, or services built directly on MegaMek’s data—such as commercial army builders or subscription-based databases—will not be permitted, as these uses violate the new license, Microsoft’s Game Content Usage Rules, and commercial rights held by Microsoft for electronic BattleTech games and The Topps Company, Inc. for the BattleTech universe.

Understanding the New Licenses

Here’s a quick breakdown of the licenses:

  • GPLv3, covering our code, allows free use, modification, and sharing of the software. Modified code must be distributed under GPLv3, including source code, ensuring ongoing community access.

  • CC-BY-NC-SA-4.0, covering our suite’s data and assets, permits free non-commercial use and modification with attribution. Modified data must remain under the same license. This is ideal for creative content.

Both licenses ensure modifications remain open to the community, aligning with our project’s core philosophy.

Timeline and Contributor Impact

We’re providing a 60-day advisory period starting today. Here’s our timeline:

  • May 19, 2025: Version 0.50.06 released (current version under existing licenses)
  • May 19, 2025: 0.50.07 development cycle began
  • From today’s blog post: 60-day community feedback period begins
  • During development: Gradual implementation of new licensing
  • Early September 2025 or later: Version 0.50.07 released under new licenses

We want everyone to have ample time to understand and raise any concerns.

How This Affects Contributors

  • Code Contributors: Your GPLv2 “or later” clause already permits upgrading to GPLv3 without additional permission—no action is needed.

  • Data and Asset Contributors: Transitioning to CC-BY-NC-SA-4.0 requires explicit consent. We’ve been actively contacting past contributors. If you haven’t heard from us yet, please reach out at megamekteam@gmail.com during this period. Your consent matters to us.

If consent isn’t given or contributors cannot be reached, we may remove or replace those contributions to ensure compliance.

Future contributions will clearly state licensing upfront—code under GPLv3 and data/assets under CC-BY-NC-SA-4.0.

Impact on Projects Using MegaMek Data

Projects using MegaMek data should review these license changes carefully. We strongly recommend consulting a legal professional to ensure compliance. The 60-day notice period provides time for affected projects to adapt.

Respecting the BattleTech Universe

These changes help us respect intellectual property rights owned by Microsoft (electronic BattleTech games) and The Topps Company, Inc. (the BattleTech universe). Catalyst Game Labs produces tabletop game materials under license from Topps.

Questions or Concerns?

For questions, feedback, or clarification, reach us on Discord at discord.gg/megamek or email megamekteam@gmail.com. We’re here to support you through these changes.

Looking Forward

These licensing updates set MegaMek up for another 20 years of growth, respecting our open-source heritage and the BattleTech universe we all cherish.

Thank you for being an essential part of this amazing community. MegaMek thrives because of players like you.

See you on the battlefield!

The MegaMek Development Team

MechWarrior, BattleMech, ‘Mech, and AeroTech are registered trademarks of The Topps Company, Inc. All Rights Reserved. Catalyst Game Labs and the Catalyst Game Labs logo are trademarks of InMediaRes Productions, LLC.

MechWarrior © Microsoft Corporation. MegaMek was created under Microsoft’s “Game Content Usage Rules” and is not endorsed by or affiliated with Microsoft.