Github would be a networking service for developers through the software code. Gitorious seems not to have such community, I guess. A lot of open source projects on github attracts those people.
If you want the positions in Japan, there are a lot of candidates because we need english speaking developer/geek.
For example, these would be the famous examples including GREE and DeNA: http://www.quora.com/Are-there-any-tech-startups-in-Tokyo
The average salary probably is 4m-6m yen/year (about $7000).
I am from Japan. Hatena Bookmark, social bookmarking community like digg, would be the biggest community where Japanese hackers share information though it is only by Japanese.
http://b.hatena.ne.jp/
