From the Ardour page on VST support:
"Please note that it is illegal to build Ardour 2.0 with VST support and then distribute the binary to anyone else. This is because Steinberg continues to refuse to allow redistribution of the otherwise freely available VST SDK. It is therefore not possible for you to comply with the terms of the GPL (i.e. you cannot provide the person you distribute the binary to with all the source code required to build the binary). We hope that one day Steinberg/Yamaha will change the licensing to allow redistribution of the SDK, and then this silly restriction will go away."
OK, so you can't build Ardour with VST support and _give the binaries_ to a commercial studio. I don't see anything in there prohibiting a studio from building Ardour _themselves_ and using it (thus no redistribution is happening).
I don't see anything in that text that says you can't make music commercially with a VST plugin via that route.