License incompatibility

[julianyon]

Carla's stated licence is GPLv2 or later, while the open source VST3 code is GPLv3.

It seems to me that if Steinberg's VST3 SDK is being used – and a quick scan of the source tree suggests that it is (source/includes/vst3sdk/LICENSE.txt) – this implies that Carla must be GPLv3 licensed, as it is the only compatible combination.