If you want your WordPress plugin/ WordPress Theme/ any code to be open for everyone, you generally have several open-source licenses to choose from. The choice of license depends on your preferences and the level of freedom you want to grant to users regarding the use, modification, and distribution of your plugin. Here are a few commonly used open-source licenses:

1. GNU General Public License (GPL):
   • GPL is a widely used open-source license. It ensures that any derivative works also remain open source.
   • WordPress itself is licensed under the GPL, making it a common choice for plugins.
   • There are different versions of the GPL (e.g., GPL-2.0, GPL-3.0), so choose the one that aligns with your preferences.
2. MIT License:
   • The MIT License is permissive and allows users to do anything they want with your code as long as they include the original copyright and license notice in any copy of the work or substantial portion of it.
   • It’s more permissive than the GPL, allowing for more flexibility in how the code is used.
3. Apache License 2.0:
   • Apache 2.0 is a permissive open-source license that allows users to use the software for any purpose, to distribute it, to modify it, and to distribute modified versions of the software under the terms of the license.
   • It has some additional protections compared to the MIT License.
4. BSD License:
   • The BSD License is a permissive free software license written by the University of California, Berkeley.
   • Like the MIT License, it allows for almost unrestricted use and redistribution.

When selecting a license, it’s crucial to understand the implications of each and how they align with your goals for the plugin. Also, consider if you want to require modifications to be open source (as in the case of GPL) or if you’re more comfortable with a permissive license that allows for proprietary modifications.

Including a clear and concise license file in your Git repository helps communicate the terms under which your plugin is distributed and used. Make sure to consult with legal professionals if you have specific concerns or questions about licensing.