By purchasing Workflow Actions Pack for Microsoft 365 you achieve annual subscription. The subscription is linked to SharePoint Online domain (yourdomain.sharepoint.com). You can use the product on any number of sites and site collections within your SharePoint Online domain. The subscription includes one year of Standard Support Plan. The workflow actions will stop working after subscription expiration.
You can purchase renewal from your shopper account.
By purchasing Workflow Actions Pack for SharePoint 2013 / 2016 / 2019 / SE you achieve a perpetual license. One license is linked to one Web Front End server (WFE). You need to purchase as many licenses as WFE servers you have. Find more information about WFE servers in in this article . The license is perpetual, but you can renew it to get one more year of Standard Support Plan and updates.
You can purchase renewal from your shopper account.
The same applies to Development license, except it can be installed to development or testing servers only.