This reminds me of the Visual Interface Dialect (VID) that is part of Rebol/View - http://rebol.com/docs/easy-vid.html

Here's the buttons examples in VID...

    Rebol []

    shrink: does []
    grow: does []

    view layout [
        text "Hello Brave New World"

        below   ; not really needed as this is the default behaviour
        button "Press Me" [shrink]
        button "No, press me" [grow]

        ; row
        across
        button "Press Me" [shrink]
        button "No, press me" [grow]
        return
    ]

VID runs on Rebol 2. Its successor (still in beta) is R3GUI which runs on Rebol 3 - http://www.r3gui.com/

This is how the buttons work in R3GUI...

    button "Press Me" on-action [shrink]
    button "No, press me" on-action [grow]

... which is even more similar to posted article.

Below is a basic (ie. naive!) boilerplate of the Todos example code in VID:

    todos: ["todo 1" "todo 2" "todo 3"]

    ;; To be defined!
    nothing: []
    controls: []
    input-zone: []

    todo-list: does [
        compose [text-list (todos)]
    ]

    footer: does [
        either empty? todos [nothing] [controls]
    ]

    view layout compose [
        label "todos"
        (input-zone)
        (todo-list)
        (footer)
    ]

NB. Disclaimer - my VID experience is very limited :)