The core team members over the years:
Pekka Klärck (né Laukkanen)    2005 -
Juha Rantanen                  2005 - 2011
Lasse Koskela                  2005 - 2006
Janne Härkönen                 2006 - 2012
Sami Honkonen                  2006 - 2007
Antti Tuomaala                 2006
Ran Nyman                      2007 - 2010
Heikki Hulkko                  2007 - 2009
Anna Tevaniemi                 2008
Kari Husa                      2009 - 2011
Jussi Malinen                  2010 - 2015
Mikko Korpela                  2010 - 2014
Ismo Aro                       2010 - 2012
Ilmari Kontulainen             2010 - 2013
Tommi Asiala                   2012
Mika Hänninen                  2012 - 2013
Tatu Kairi                     2012 - 2014
Anssi Syrjäsalo                2013
Janne Piironen                 2013 - 2014

Other contributors:
Elisabeth Hendrickson          Quick Start Guide (2.0)
Marcin Michalak                String library (2.1)
Chris Prinos                   reST (HTML) support (2.1)
                               How-to debug execution with `pdb` (2.7.6)
Régis Desgroppes               Fixing installation paths (2.1.3)
                               xUnit compatible outputs (2.5.5)
Robert Spielmann               Report background colors (2.5)
Xie Yanbo                      Alignment of east asian characters (2.5.3)
JSXGraph Developers            JSXGraph tool and license changes for it (2.6)
Imran                          Template names to listener API (2.6)
                               Suite source to listener API (2.7)
Tatu Aalto                     Get Time keyword enhancement (2.7.5)
Eemeli Kantola                 Fix for non-breaking spaces (2.7.5)
Martti Haukijärvi              IronPython support to Screenshot library (2.7.5)
Guy Kisel                      How-to use decorators when creating libraries (2.7.7)
                               BuiltIn.Log pprint support (2.8.6)
                               New pattern matching keywords in Collections (2.8.6)
                               Keyword/variable not found recommendations (2.8.6)
                               Tidy ELSE and ELSE IF onto separate lines (2.8.7)
                               Initial contribution guidelines (2.9, #1805)
Mike Terzo                     Better connection errors to Remote library (2.7.7)
Asko Soukka                    reST (plain text) support (2.8.2)
Vivek Kumar Verma              reST (plain text) support (2.8.2)
Stefan Zimmermann              **kwargs support for dynamic libraries (2.8.2)
                               **kwargs support for Java libraries (2.8.3)
                               *varargs support using java.util.List (2.8.3)
Mirel Pehadzic                 Terminal emulation for Telnet library (2.8.2)
Diogo Sa-Chaves De Oliveira    Terminal emulation for Telnet library (2.8.2)
Lionel Perrin                  Giving custom seed to --randomize (2.8.5)
Michael Walle                  Telnet.Write Control Character keyword (2.8.5)
                               Telnet.Read Until Prompt strip_prompt option (2.8.7)
                               String.Strip String (3.0)
Tero Kinnunen                  BDD 'But' prefix ignored (2.8.7)
Heiko Thiery                   Enable log level config option for TelnetLibrary (2.8.7)
Nicolae Chedea                 Float parameters in FOR IN RANGE (2.8.7)
Jared Hellman                  Custom keyword names (2.9)
                               Embedded arguments for library keywords (2.9)
Vinicius K. Ruoso              Support multiple listeners per library (2.9)
                               Allowing control over connection timeout in Telnet library (2.9.2)
                               Supress docutils errors/warnings with reST format (2.9.2)
Joseph Lorenzini               Exposed ERROR log level for keywords (2.9)
Guillaume Grossetie            Less flashy report and log styles (2.9, #1943)
Ed Brannin                     FOR ... IN ZIP, FOR ... IN ENUMERATE (2.9, #1989)
Moon SungHoon                  String.Get Regexp Matches keyword (2.9, #1985)
Hélio Guilherme                Support partial match with String.Get Lines Matching Regexp (2.9, #1836)
Jean-Charles Deville           Make variable errors not exit `Runner keywords` (2.9, #1869)
Laurent Bristiel               Convert examples in User Guide to plain text format (2.9, #1972)
Tim Orling                     IronPython support for `Dialogs` library (2.9.2, #1235)
Jozef Behran                   Fix ${TEST_MESSAGE} to reflect current test message (3.0, #2188)
Joong-Hee Lee                  Extend 'Repeat Keyword' to support timeout (3.0, #2245)
Anton Nikitin                  Should (Not) Contain Any (3.0.1, #2120)
Yang Qian                      Support to copy/deepcopy model objects (3.0.1, #2483)
Chris Callan                   Case-insensitivity support to various comparison keywords (3.0.1, #2439)
Benjamin Einaudi               Add --rerunfailedsuites option (3.0.1, #2117)
Traitanit Huangsri             Support more glob-like patterns for test filtering (3.1, #2471)
Brian-Williams                 Named-only arguments support with Python 3 libraries (3.1, #2555)
Élysson Mendes Rezende         Add format_string keyword (3.1)
