It sounds like network rendering isn’t free anymore.

That is correct. Network rendering ceased to be free with V-Ray 3 several years ago, and now that same policy is being applied to V-Ray for Cinema 4D. The new 3.7 version can now leverage the same universal V-Ray Render Node licenses that our other V-Ray products also use. If you already own universal V-Ray Render Node licenses that you purchased from Chaos Group, you will be able to use those with V-Ray 3.7 for Cinema 4D.