Page Builder is licensed under GPL 3.0. You can read through license.txt in the plugin folder for full license details. The GPL license allows for relatively unrestricted personal and commercial use.
You can also bundle Page Builder with themes you’ve authored, provided the theme is licensed under GPL. You’re even allowed to sell your theme. If you want to sell your theme on ThemeForest, you’ll need to ensure that you select the GPL licensing option. Their standard license is not GPL-compatible. That said, we suggest encouraging your users to install Page Builder from the WordPress plugin repo. Doing so will ensure they stay updated with the latest version of Page Builder. It’s an actively developed plugin with regular updates and bug fixes.