Fair - the aggregate clause does say “larger program” so I overstated. However, it doesn’t define combination, and “based on the Program” is defined in section 0 via copyright permission - which is why I keep returning to copyright rather than mechanism.

The JS client doesn’t call into scsynth code. In postMessage mode the client and the engine run in separate execution contexts with no shared memory, exchanging serialised OSC - the browser enforces that boundary the same way the kernel does between processes on a socket.

Also, the JS and Erlang clients are entirely my own code and copyright surely their licence isn’t in question. I think the question you’re actually raising is what obligations fall on users who combine their software with SuperSonic. You already state that my approach in Sonic Pi is fine.