I'm not sure, but I thought that you had to pay for a Redhat license if you want to use Redhat. Perhaps that is only if you want to use it for commercial purposes. If you are, then you should probably look into that. There are two other versions of Linux that would work as well. Centos is essentially a free clone of Redhat. You don't get the same support that you would get if you had a Redhat license, but it is essentially the same. There is also Scientific Linux, which is sponsored for the Fermi National Accelerator Lab.
https://www.scientificlinux.org/
Scientific Linux does have some differences in libraries, but it should work the same. Generally Redhat and Redhat clones use YUM for maintaining packages. I have Ubuntu at home. I have Oracle 11.2.0.2 installed and running, as well as mySQL, and a test version of Request Tracker that I am testing. It works fine for what I need. It just has more user friendly packages along with things that you would need for databases or web servers.