Do you have any silent installation options? I have tried the normal /s after the exe executable but it still asks you to agree at the license page.
Shotcut is free, open source software - no license required. Try downloading it from https://shotcut.org/download/.
There’s the GPL license that you agree to in the beginning.
Judging by the .nsi source file - no. The NSIS installer framework provides limited silent install features out of the box; specifically, using /S sets a few flags that can be checked with e.g. IfSilent to run specific code blocks, as opposed to other (generally less flexible, and certainly less open) frameworks that are sufficiently limited that they require you to specify a default option for everything, which is then used in silent installs unless overridden. Often installers need more flexibility than that and require getting command line option-value pairs and parsing them manually, then making the appropriate decisions from there in the code.
It wouldn’t be hard to add a silent install option, but I’d guess the GPL license page was set up for a reason, and might need a command like flag to indicate that the GPL is accepted. Though often silent installs are managed and automated (e.g. ninite’s approach) at which point whether or not the license was actually accepted by the end user is dubious at best 
There’s the GPL license that you agree to in the beginning.
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Oops , sorry, I assumed it was some kind of commercial licence.
If you want a silent install, then use the portable version. The installer only does little more than uncompress: writes a registry entry and creates an icon in start menu.
I found the the parameter needs to be a capital S. So it should be:
exename /S
/s shows the GPL screen