The JUCE library itself is licensed according to its own licence agreement (or an alternative agreement you might have with PACE).
The rest of the template code and scripts are released in the public domain. Any acknowledgement of my work is appreciated but not required.
The VST support is now included with JUCE. Please make sure you are aware of the licensing terms associated with using VST SDKs before proceeding. The AAX SDK can be obtained separately from Avid, for which you need a separate agreement, as well as PACE signing tools. Please check JUCE/sdks/SDKS-FOLDER-README.md for more information.
George