Marko Heijnen is a long-time WordPress core contributor and GlotPress lead developer. His last major contribution to WordPres swas the abstraction of image editing called WP_Image_Editor. He now start working for hosting company 1&1 where he will help out improving their platform for a better experience when using an open source CMS. He still will contribute a part of his time to open source platforms like WordPress and Drupal.
Beside working for clients he spends a lot of time building a project for artists called ArtistPress and open source plugins like: Improved image editor, Tabify Edit Screen and WP DB Drivers. This all for WordPress.