No, you won’t be charged to access their fork on Github. If you want them to host your Elastic or Kibana service you’d have to pay for the service, but that’s not related to access to the Apache licensed source code.
From the article:
"Our forks of Elasticsearch and Kibana will be based on the latest ALv2-licensed codebases, version 7.10. We will publish new GitHub repositories in the next few weeks. In time, both will be included in the existing Open Distro distributions, replacing the ALv2 builds provided by Elastic. We’re in this for the long haul, and will work in a way that fosters healthy and sustainable open source practices—including implementing shared project governance with a community of contributors."
Aren't they sharing the fork? Sounds more like "we like it but its no longer free to use, so we're making it free. btw you can pay us to host it for you"
While what AWS is doing is (probably, IANAL) within their legal rights, it's arguably immoral because it is basically saying, "We love this project so much we're going to build it into a different direction and charge people to access our version." Which, given AWS's widespread adoption, puts the OS version in peril.
Edit: Thanks for pointing out that AWS will be releasing the code under an Apache 2 license. That does change my opinion somewhat, though I'll leave my original comment for posterity.