These free themes were researched and compiled by fris, find him on GitHub

1. AngularJS WordPress Theme – used for building single page client side applications using WordPress
   https://github.com/royboy789/Angular-Wordpress-Theme
2. Starter theme using Composer, Grunt, and Bower
   https://github.com/wpsitecare/alpha
3. WordPress theme that renders JSON for consumption by AJAX or cURL
   https://github.com/underblob/JSON-WordPress-Theme
4. Power your reveal.js presentation with WordPress
   https://github.com/alleyinteractive/revealjs-wp-theme
5. A WordPress starter theme built off _s and the JSON REST API Backbone client.
   https://github.com/tlovett1/_s_backbone
6. Soblossom is a WordPress starter theme that is based on Foundation
   https://github.com/senlin/soblossom
7. WordPress Genesis Framework child theme using Bootstrap front-end framework.
   https://github.com/brandonhimpfen/wordpress-genesis-bootstrap
8. A Wordpess starter theme based on Bones and Bootstrap 3
   https://github.com/slightlyoffbeat/brew
9. Wolf is a SASS-based starter theme for WordPress
   https://github.com/bradp/wolf
10. A WordPress starter theme built with Genesis and Foundation
    https://github.com/joshmedeski/rootbeer
11. _s + Gulp starter WordPress theme
    https://github.com/braginteractive/kickoff
12. _s + Gulp + Bower starter WordPress theme
    https://github.com/braginteractive/kickoff-bootstrap-3
13. Wordpess starter theme with twitter bootstrap, HTML5 boilerplate and Schema.org
    https://github.com/overclokk/ItalyStrap
14. A basic WordPress theme based on angular js
    https://github.com/tarex/Angular-WordPress-Theme
15. A presentation theme that uses the REST API
    https://github.com/jacklenox/picard-present
16. AngularJS And WP REST API WordPress Theme
    https://github.com/1fixdotio/angularjs-demo-theme
17. A bare-bones AngularJS blog app designed to work with the WordPress JSON REST API.
    https://github.com/michaelbromley/angular-wordpress-seed
18. FoundationPress is a WordPress starter theme based on Foundation 6 by Zurb
    https://github.com/olefredrik/foundationpress
19. _s WordPress Starter Theme + Bootstrap SASS
    https://github.com/holger1411/understrap
20. A Bootstrap Underscores WordPress Theme with Font Awesome
    https://github.com/ZacharyChim/zacklive
21. A WordPress Theme Using _s, Bourbon + Neat and Theme Hook Alliance
    https://github.com/digisavvy/some-like-it-neat
22. A Genesis Starter Theme built using Bourbon and Neat
    https://github.com/digisavvy/genesis-bourbon-neat
23. Bourbon, Neat, Bitters, and Refills WordPress Theme
    https://github.com/braginteractive/hooch
24. A WordPress theme built with Backbone that uses front-end routing.
    https://github.com/trevanhetzel/backbone-wp
25. WP-API Photo Blog Theme
    https://github.com/mattheu/mph-photos
26. Feelingrestful WordPress React JS theme
    https://github.com/humanmade/feelingrestful-theme
27. WordPress Starter Theme That Uses Brunch, Bower, And Bootstrap
    https://github.com/hyyan/brunch-wordpress-theme
28. A template for creating WordPress themes using Gulp with Jade, Sass, and Compass and support for Bootstrap.
    https://github.com/ajschlosser/wordpress-jade-bootstrap-template
29. Bootstrap 4 WordPress Theme
    https://github.com/braginteractive/strappress
30. Angular app that uses the WP REST API
    https://github.com/braginteractive/ngWP
31. Emi, a WordPress Starter Theme with Gulp, and SASS
    https://github.com/zoerooney/Emi
32. A developer-friendly WordPress base theme built with UIkit and GulpJS
    https://github.com/zslabs/basey-theme
33. A WordPress theme powered by the WordPress REST API and Vue.js
    https://github.com/gilbitron/wp-rest-theme
34. WordPress theme using Angular.js and Bootstrap Frameworks
    https://github.com/tomtom87/angular-bootstrap
35. AngularJS and WordPress co-existing
    https://github.com/studioraygun/angularwp
36. {{mustache}} starter theme for WordPress
    https://github.com/cjonasw/wordpress-starter-theme-mustache
37. Jade starter theme for WordPress
    https://github.com/cjonasw/wordpress-starter-theme-jade
38. Starter child theme for the Genesis Framework using Sass and Grunt
    https://github.com/BeardedGinger/Genesis-Starter-Child-Theme
39. A react-based recipe theme for WordPress
    https://github.com/ryelle/Anadama-React
40. Starter SPA front-end backed by the WordPress REST API
    https://github.com/shelob9/josie
41. A stripped down example of a WordPress theme that uses Backbone.js
    https://github.com/tollmanz/backbone-wordpress-theme
42. Toolkit theme for WordPress, based on Hybrid Core and Twitter Bootstrap and Twig
    https://github.com/Rarst/hybrid-wing
43. Starter WordPress theme. Using Gulp, Browserify, NPM (for dependencies available) and Sass
    https://github.com/trevanhetzel/wp-starter
44. An Advanced Gulp Workflow for WordPress themes
    https://github.com/ahmadawais/advanced-gulp-wordpress
45. A theme to demonstrate simplest implementation of WPGulp Boilerplate
    https://github.com/ahmadawais/WPGulpTheme