Wayland

http://cgit.freedesktop.org/wayland/wayland/tree/src/wayland-client.h
http://cgit.freedesktop.org/wayland/wayland/tree/src/wayland-server.h
http://cgit.freedesktop.org/wayland/wayland/tree/src/wayland-egl.h

That's it. Those three tiny header files is all you need to be able to host or interface with a Wayland server, create and manipulate windows, get input device events, or get an EGL context for use with OpenGL or OpenGL ES (your choice). There are no configuration files (everything is autodetected and/or delegated to the kernel, enumerating display adapters, adapter outputs, input devices, etc. is done by traversing the mounted devfs file system tree).

You can use this as your starting point to implement a full blown DWM or X Windows layer, or you can use it write client applications that integrate nicely with any active Wayland server including Wayland-based DWM.

Why are you still using X Windows?

>>11
It relies on the cooperation of the authors of every app running on your desktop to get an even remotely consistent interface.
I'm not concerned there. Many applications provide their own decorations already. It's not like you can stop people from being assholes. This is the one valid concern you have, even if it is already a problem today.

Now every program has to link to a GUI toolkit
The vast majority already do. Games tend to have in-game menus and don't need the toolkit anyway—part of the design of Wayland is to permit windows to exist framelessly. The toolkits don't even work in fullscreen.

The window manager can no longer force window resizing
That has nothing to do with decorations unless maybe you don't have an alt key. My windows have no borders BTW.

and closing to work for programs that stop responding to messages.
Programs can refuse to close as it is.

It clashes with the current system, which is sure to make it harder to write something that works with both.
This is sort of true. X apps are supposed to run in an X-server as a Wayland client. That might sound terrible, but it fits perfectly with X mentality. And it works.

Hearing Wayland supporters talk about how everyone will just use libraries and that will solve everything is like hearing libertarians talk about the Invisible Hand of the Free Market.
It's not though. Those libraries exist and they're not invisible. The challenges are being taken up by real people doing real work.