Is this what you want? (.odkbuild file, try loading it into ODKBuild)
{"title":"username","controls":[{"name":"name","kind":"Username","metadata":{},"type":"metadata"},{"name":"showusername","label":{"0":"your name is"},"hint":{},"defaultValue":"","readOnly":false,"required":false,"requiredText":{},"relevance":"","constraint":"","calculate":"/data/name","length":false,"invalidText":{},"metadata":{},"type":"inputText"}],"metadata":{"version":2,"activeLanguages":{"0":"English","_counter":0,"_display":"0"},"optionsPresets":[],"htitle":null,"instance_name":"","public_key":"","submission_url":""}}