According GoDaddy's WordPress Hot 100, Divi and Zerif were included in Top Themes for August 2017.
You can install Divi theme on any number of websites without limitation. However, Zerif Pro has some restrictions.
Just for your reference, Zerif Pro is only available as part of the membership. There are three kinds of memberships:
Treasure Chest Lite and Treasure Chest are identical except the membership term: 1 year vs. 2 years. Private Club is a lifetime membership and allows users to install themes on up to 5 domains.
Treasure Chest Lite and Treasure Chest memberships offer:
- 1 Year / 2 Years of Free Updates
- For up to 3 Domains
- Access to All 20+ Themes
- Access to All 10+ Plugins (1 Site License)
- Access to New Themes & Plugins
- 1 Year Shared Hosting
- Fast & Friendly Support
It's interesting that 1 year shared hosting is included in the membership.
It's not clear whether users can install themes and plugins on any number of websites or not. And what does "for up to 3 domains" mean? Regarding this, please refer to the following answer from Themeisle staff:
Hello, up to 3 sites means a single theme can only be activated on one website (including subdomains) at a time. You can install the themes on any number of sites you wish, it's just that only 3 sites will be able to be activated at a time.
Each theme comes with 3 licenses.
For the plugins, you get all our plugins but instead 1 license per plugin, you can purchase the plugins individually if you need additional licenses.
Therefore, you can install themes on a number of websites, but each theme can be activated only on 3 sites since it has 3 licenses. Each plugins comes with 1 license only and you can each plugin only on one domain.
You may want to use Zerif Lite before purchasing a membership. I think Elegant Themes (Divi) offers more flexible plans.