Precisely.
Apple's new OS is officially called OS X 10.4. "Tiger" was its development code name that has spilled over into the marketing. Big deal.
Tiger Direct might get an injuction requiring Apple to cease and desist from publicly referring to the OS as "Tiger", but they'll never be able to interfere with the roll out.
And Tiger Direct will never be able to stop the general public from referring to the OS as "Tiger".
And their timing couldn't be more suspicious. After all this OS has been referred to as "Tiger" for at least a couple years now.
It is a big deal. It's just as you said. It was an internal development code name and should have stayed an internal development code name. If it had there would be no lawsuit. But once Apple starts marketing it as "Tiger" and since TigerDirect has a trademark on "Tiger" used on software, they now have a legitimate case.