Subfolder network can use 1 plugin license per network.
Plugin must be activated network wide and license should be activated at primary website:
One license work only with 1 WP Multisite subdomain website instance.
Why a license activation on a multisite network isn’t considered as a single activation?
Multisite networks are way more complex than standard WordPress installations, have significantly more edge cases, and a higher chance for conflicts as subsites in the network can run different combinations of plugins and themes.
Also, multisite-networks are largely used by bigger entities like agencies, boutique hosting providers, and WaaS, who generate revenue from their networks and, therefore, have higher load to us .
Consequently, it’s only fair to charge them more for protecting each WPMU website instance.