OK, I'm gettin mad!
When I install the rpm right now it says:
Preparing ############################## [100%]
Operating system is Mandrake-LinuxUpdating / installing
webmin-1.470-1pclos2009.noarch ############################## [100%]
Webmin install complete. You can now login to
http://localhost:10000/as root with your root password.
But, when I run it, it still says generic and all the paths are wrong! AAAAArrrgg!
BTW: I'm getting now why the texstar does things the PCLOS way! Solved the tmp folder permissions issue with
%{_tmppath} 
-----------------------------------
Update:
1. Now the temp files in src/tmp are owned by root so I still have to go in and delete them as root after every build.
2. The oscheck in the spec file only announces the OS during install, it has nothing to do with how the build detects it.
3. I suspect the oscheck needs root access, though I don't know why it should, I will try building this as root on my testbox and see if it makes a difference.