if I understand correctly the rethink app does also work as a firewall , so no . I've also found netguard to be less intuitive and to have a less readable UI .
if you are just using rethink as a DNS provider however then netguard (or the rethink app) can allow you to have more granular control over specific apps .
not entirely sure but this doesn't feel like something the fsf would like . most definetly it violates freedoms 0. because it discriminates against companies with over 5 M$ in income and against people living in Japan (see 2.14 , though I'm not sure its enough to qualify) , and possibly by restricting what you can do with the software , though I'm not sure on that one . it also violates freedoms 2. and 3. by requiring publicly releasing your changes (fsf requires that free software licenses allow for private modifications) and possibly by requiring contacting the licensor or the post-open administration though I'm unsure of if it does (entering into a post-open source zero-cost / paid contract seems to me to imply contacting either the licensor or the post-open administration) .
further reading :