If you buy a plugin project which has issued lifetime licences, you are aware of that before making the deal. If those lifetime licences are a problem for you, don’t buy the plugin project or negotiate a buying price which covers that problem. Ongoing development costs are priced in, deal with it. Or take it as a learning curve for your business capabilities if you did not think about that before.

Sidenote, the links in that newsletter (and a newsletter before) are redirected through some shady third party tracking company without any mention nor consent from newsletter subscribers. Voids GDPR regulations. Delicious Brains has been notified about that before, no reaction.