In regard to the protection of blueprints and materials, those graphs have the ability to collapse selected nodes to functions or macros. That would be sufficient (minimal and unintrusive) protection for me if those collapsed nodes could remain locked and not viewable with a double-click to open.
A purchaser would be free to edit any other nodes in the graph, e.g maps.
That would be a fair compromise for both the author and client:
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Client is not penalised by heavily intrusive DRM and has artistic flexibility to adapt blueprint/material to their own project.
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Author can protect specialised functions that do not have to be seen in order to use the blueprint or material.
Unfortunately, this scheme does not protect models, sounds or textures which must be viewable in their entirety at all times.