David Heinemeier Hansson extracted Ruby on Rails from his work on Basecamp. He released the framework as open source in July of 2004, but didn’t share the commit rights until February of 2005. He’s infamous for his ruthless delegation, which is often executed as a request to “Please Do Investigate”. He’s a partner at Basecamp, his personal page is heinemeierhansson.com, and you can follow him on Twitter @dhh.
Jeremy Daer is a programmer at Basecamp hailing from Pasadena, California. Hot on the heels of DHH, he has been the most active contributor to Rails. He’s knee deep in pretty much all aspects of the framework and one of the top batters against new, incoming tickets. You can follow him on Twitter @bitsweat.
José Valim is the lead-developer and co-founder of Plataformatec. He started working with Rails in late 2006 and began contributing actively after his Google Summer of Code project in 2009. He’s frequently flying between Brazil and Poland, some say that it is his “eureka” time to code and bring new open-source projects to life. Check for yourself what he’s up to on his company’s blog.
By day, Aaron Patterson (tenderlove) is a mild mannered programmer for Red Hat whose Ruby code is almost as good looking as him. By night, he dons his Pink Warrior suit which gives him the power to contribute to many Open Source projects such as nokogiri, Ruby, and Rails. If you have seen someone kissing Matz or DHH at a conference, it was probably him. You can find him on twitter, or read his blog.
Xavier Noria is an everlasting student and father of the most wonderful girl, as the picture to the left clearly demonstrates QED. An independent Ruby on Rails consultant from Barcelona, Xavier has worked with Rails since 2005. He wrote Rails Contributors and has been a regular contributor for years. Honored to have been presented a Ruby Hero Award. Xavier is @fxn on Twitter.
Rafael França is a member of Shopify's development team. He has worked full time with Rails since 2010 and has been contributing to the framework since the beginning of 2012. As a result of being passionate with OSS, he performs a key role in maintaining Simple Form) and also contributes to many other projects. Follow him on Twitter, on Github.
Guillermo Iguaran began using Ruby in 2008 and has been working with Rails since 2009. He started contributing to Rails framework and open-source world in 2011. Guillermo is from Colombia and right now he’s working as Software Engineer at Ride, and completing his Computer Sciences master’s degree. You can follow him on Twitter or Github.
Carlos Antonio is a software developer at You Need A Budget (YNAB). He started working with Ruby and Rails in late 2007, and since then he has become an Open Source lover, contributing to many different projects, and maintaining libraries like Simple Form and Devise. His motto is Hacking Beautiful Code. You can follow him on Twitter, or check his Github.
Godfrey Chan is a staff engineer at Tilde based in Portland, Oregon. He began contributing to Rails in 2012. In addition to his code contributions, he enjoys connecting with others in the community through speaking at conferences, volunteering for RailsBridge and sending newsletters. You can follow him on Twitter or Github.
Rails core members who are no longer active in the day-to-day stuff have been immortalized as core alumni.