language outside Japan. In this same year, Matsumoto and Keiju Ishitsuka wrote the first book on Ruby, The Object-oriented Scripting Language Ruby (オブジェクト指向スクリプト言語 Ruby), which was published in Japan in October 1999. It would be followed in the early 2000s by around 20 books on Ruby published in Japanese. By 2000, Ruby was more popular than Python in Japan. In September 2000, the first English language book Programming Ruby was printed, which was later freely released to the public, further widening the adoption of Ruby amongst English speakers. In early 2002, the English-language ruby-talk mailing list was receiving more messages than the Japanese-language ruby-list, demonstrating Ruby's increasing popularity in the non-Japanese speaking world. Ruby 1.8 and 1.9 Ruby 1.8 was initially released August 2003, was stable for a long time, and was retired June 2013. Although deprecated, there is still code based on it. Ruby 1.8 is only partially compatible with Ruby 1.9. Ruby 1.8 has been the subject of several industry standards. The language specifications for Ruby were developed by the Open Standards Promotion Center of the Information-Technology Promotion Agency (a Japanese government agency) for submission to the Japanese Industrial Standards Committee (JISC) and then to the International Organization for Standardization (ISO). It was accepted as a Japanese Industrial Standard (JIS X 3017) in 2011 and an international standard (ISO/IEC 30170) in 2012. Around 2005, interest in the Ruby language surged in tandem with Ruby on Rails, a web framework written in Ruby. Rails is frequently credited with increasing awareness of Ruby. Effective with Ruby 1.9.3, released October 31, 2011, Ruby switched from being dual-licensed under the Ruby License and the GPL to being dual-licensed under the Ruby License and the two-clause BSD license. Adoption of 1.9 was slowed by changes from 1.8 that required many popular third party gems to be rewritten. Ruby 1.9 introduces many significant changes over the 1.8 series. Examples include: block local variables (variables that are local to the block in which they are declared) an additional lambda syntax: an additional Hash literal syntax using colons for symbol keys: per-string character encodings are supported new socket API (IPv6 support) require_relative import security Ruby 2 Ruby 2.0 was intended to be fully backward compatible with Ruby 1.9.3. As of the official 2.0.0 release on February 24, 2013, there were only five known (minor) incompatibilities. Ruby 2.0 added several new features, including: method keyword arguments, a