Do copyrights and DRM inhibit the spread of knowledge?
Inherently, that's what they are intended to do.
DRM locks content away until you pay the publisher to use it, thereby preventing derivative works, and exposure to the general population which are either uninterested, or at least not interested enough to pay for it.
Copyright locks methodology & knowledge away, and prevents others from either using it, or creating derivatives of it .. thereby halting any progress with it .... unless anyone who wants to use itvto make something, or further develop it either pays a small fortune to the original patenter ... or risks future, possibly devastating, financial penalty.
DRM should be illegal. Copyright should have very short lifespan (1-2years).