Hi @terocha, thanks for your question.
Using the same email is definitely fine, there’s no limit to the amount of free sites the same email address can register. However, each site should have a separate key.
Any sites installed before the free license changes will have a key generated automatically by Wordfence, which will still work fine. However, the only current way to get additional free keys for all your sites is to go through the free API Key process: https://www.wordfence.com/help/api-key/#installing-your-free-license-key
The main problem of the same key making its way on to multiple sites is that some actions are rate-limited by key on our servers when requests come in, so too many sites making API calls for rule updates with the same key may not succeed.
Thanks,
Peter.
