The code for logstash lives on github, but everything else in the project lives on googlecode (wiki, issues, downloads)
If you want to learn about logstash, check out the main project site here:
http://code.google.com/p/logstash/
File bugs here: http://code.google.com/p/logstash/issues/list
Please do not file bugs on github, the issue tracker here on github is pretty weak compared to the much better issue tracker on googlecode.