It's also that set of restrictions that won't let me release VST plug-ins using Juce, Agg 2.5 and a number of other nice GPL'ed projects, as much as I'd like to release my own source under GPL.

Or, rather it's the combination of those restrictions, and the fact that Steinberg won't allow the vstsdk headers to be distributed freely, even though anyone can download them off their site.

Either way, it means less source is released under the GPL.