Is it necessary to use JADE when building Angular Apps with Node and Express?

No it is not necessary, you can use different templating engines with Node & Express or you can just send pure HTML files.

Jade is just a default templating engine that comes with Express.js, If you want a templating engine that is close to bare html i think dust.js is a good one.

Quite frankly angular.js has nothing to do with this.

You can set up express to render pure html files like this.

app.configure(function(){  app.set("view options", {     layout: false  });  app.register('.html', {    compile: function(string, options){      return function(locals){        return string;      };    }  });});

Then just render like this

app.get('/myUrl', function(request, response){  response.render("index.html");});

or, when I was using ember on the frontend it was so conflicting to write handlebars templates in jade templates, so in my jade template I simply included a pure html file like this.

include '/handlebars/templates.html';

Yes, it is possible. Jade is a (primarily – and I imagine it’s how you’re using it) server-side template engine. Angular bases itself off the HTML served to the client; it doesn’t matter what produced it. NodeJS is just a server. Express is just a server-side framework.

Angular can even work without a server; see jsFiddle, for example.

EJS is another framework that is popular with express and is pretty close to just bare HTML.