if that text file were the preferred form to make modifications to it (AKA source code), then I guess it wouldn't deserve the "proprietary" qualifier any longer. but we have neither sources nor a suitable freedom-respecting license, and either one would be enough to make it proprietary.

but the SOF situation is entirely different from that. there is source code for the programs (though I admit to not having searched for blobs in them), and there is a free license that (purports to?) apply to them. AFAICT the only problem with SOF is the Tivoization that affects the binaries signed with the Intel-private signing key.