什么是“Red Hat Linux Advanced ”?

什么是“Red Hat Linux Advanced ”?

Oracle9i Database Release 2 on Linux: Performance, Reliability and Manageability Enhancements on Red Hat Linux Advanced Server 2.1

里面的“Red Hat Linux Advanced Server 2.1”是个什么东西?      
就是RH的高级版,想$MS的东东ADV一样      
那么它在什么地方可以DOWNLOAD?还是这东西必须付钱去买。好像ORACLE9iR2推荐在它上面安装的。      
Download is NOT AVALIABLE!

You MUST pay money!!      
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我有点不明白为什么源码开放还可以收钱,是不是要付给作者版税就行了,那linux的开发者就 。。。。。。。。。:confused:      
you can download it for free      
Where?Give me the address?
I find it in redhat ftp,but they are SRPM packege.I want ISO image!      
I don't know where you can download ISO, but you can compile all this source rpm easily.