Here is the license info for AffiliateWP, a premium Affiliate Program plugin which sells for starting at $99 per year, for 1 site:
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/**
* Plugin Name: AffiliateWP
* Plugin URI:
https://affiliatewp.com
* Description: Affiliate Plugin for WordPress
* Author: AffiliateWP, LLC
* Author URI:
https://affiliatewp.com
* Version: 2.2.11
* Text Domain: affiliate-wp
* Domain Path: languages
* GitHub Plugin URI: affiliatewp/affiliatewp
*
* AffiliateWP is distributed under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* any later version.
*
* AffiliateWP is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with AffiliateWP. If not, see <http://www.gnu.org/licenses/>.
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Here is their pricing page:
https://affiliatewp.com/pricing/
Do you think they want some asshole stripping the licensing mechanism and distributing it for free?