cat /proc/version doesn't tell me what distro I'm running

I wouldn't worry about the information in parentheses in /proc/version. It tells you about the version of GCC that the kernel was compiled on, not anything about the machine it's running on… it doesn't necessarily mean that your host is running Red Hat, although it might be a hint that the Linode admins favour RH.

For example, my vanilla non-Linode Ubuntu 6.06 kernel contains "(gcc version 4.0.3 (Ubuntu 4.0.3-1ubuntu5))" in /proc/version… It wasn't compiled on "Ubuntu 4.0.3", just Ubuntu's version of GCC 4.0.3.

I'm not sure what an "equivalent" of those commands would be, since as far as I know they are working exactly the same as normal. The same thing would happen without UML, if you were using a non-distro-supplied kernel.

If you just want to know what distro of Linux you're using, usually there's a file in /etc to tell you, with a name ending in -version or -release. Ubuntu seems to have /etc/lsb-release, which might be standard nowadays, for all I know.