Here is a little bit fancier version using simple GUI for displaying data.
true app:isgui !
"commits.json" f:slurp json> var, data
a:new var, items
var gui
{
  "kind" : "win",
  "buttons" : 5,
  "title" : "JSON Challenge",
  "wide" : 640,
  "high" : 480,
  "center" : true,
  "children" :
  [
    {
      "kind" : "table",
      "name" : "table",
      "bg" : "lightgreen",
      "hl" : "lightgray",
      "hlc" : "gray",
      "bounds" : "10,10,parent.width-10, top+460",
      "header" : [
                   { "name" : "Name of committer", "width":160 },
                   { "name" : "Date of commit", "width":160 },
                   { "name" : "The SHA HASH for commit", "width":280 }
                 ]
    }
  ]
} var, gui-desc
: app:main
  data @ ( nip "commit" m:@ "author" m:@ nip "name" m:@ swap "date" m:@ nip rot "sha" m:@ nip 3 a:close items @ swap a:push drop ) a:each drop
  gui-desc @ "children" m:@ nip 0 a:@ nip "items" items @ m:! drop
  gui-desc @ g:new gui ! ;