By itself, it's not proprietary. But, it's an enabler for a proprietary internet. The original HTTP was by nature open and "democratized" - partly because everything was in plain text.
The binary stream of http/2 is a multiplexer. It allows for the packing of binary bitstreams into a "container" connection. This is similar to the way h.264/h.265 video streams are both streams and containers for a proprietary format.
I can see the creation of a special binary format (there's nothing to stop an allegiance of commercial interests, including browser makers, from doing this) - that actually patents a special sort of binary stream used with http/2. So, to use the internet (once everything was converted) - you'd need to use patented stuff - and websites would pay royalties.
Now, you'll say that they could do this now. Yes, they could - but it would be difficult - an easy mechanism that is universally deployed is not in play yet. Will be for http/2, which paves the way for this kind of thing. As I wrote, it's the mass adoption of an enabling format that will allow for the "hog-tying of the internet."