SIP, or “system integrity protection” , it’s a features to protect some critical parts of the OSX file system.
It’s quite easy to disable SIP:
IMHO is a critical action: if you make a mistake you have to reinstall your MAC from scratch.
We have the clear evidence that the API developer has never tested the installation on Catalina or Monterey and this is really disappointing.
There is no real reason to have the SDRPlay API installed under the /usr folder: the API developer can simply modify the installation script and use a different and accessible folder.