If you pay Red Hat, you pay for the Enterprise support and the EAP version of JBoss. This EAP is based on the Community version but will have tested by Red Hat and therefore is will have a slower release cycle. Also it may not include unstable and experimental stuff.
Also with this EAP version it is possible to have a long term support. The EAP version is only available via the Customer Support Portal. You can read the Product update and Support Policy for that.
The Community version is open source and free for use, see the LICENSE.txt which come with the download archive.
You can use this version for development, at home, as productive server as you want.
The difference is that you will not get any bugfixes or security fixes. You have to upgrade to the next version, use the upstream repository and/or fix the bug by yourself. You are welcome to contribute here!
Also you will get no support, but you can ask discuss here in the community forms.