There are two main reasons for an installer to issue a message saying that the OS version is unsuited.
The first one is that the OS is more recent than the installer and the installer, not being knowledgeable about the future, has to issue the warning. In this case, you are usually allowed to ignore the warning, complete the installation but be alert to the possibility of the compiler's failing to perform properly.
The second reason, the one that applies to your case, is that the OS is too old to provide the features necessary for the software to work at all. The failure is not the fault of the installer. The installer is actually working to your benefit by preventing you from attempting an installation that is doomed to fail. Even if you were to copy the compiler package file-by-file from another installation, it would not work, just as no 32-bit compiler would work on a 16-bit OS such as MSDOS without an extender.
It's also possible that the combination of compiler and OS you chose simply hasn't been tested. You should find papers posted at the top of the forum giving advice on how to install past versions of ifort on Fedora. Current versions of ifort may install OK if you simply accept the unsupported installation (provided that you have installed the prerequisites, primarily the g++ development system corresponding (32- or 64-bit) to the compiler you wish to install. Current ifort works well with g++ 4.2 through 4.5.