Gome, a java (J2ME) based application for playing go on mobile phones, was open sourced today. Previously, this was commercial software, but the dwindling market for go software on "dumbphones" has prompted the author to release the code to the community.

See https://github.com/gbin/Gome
From the readme:

Gome is a go assistant written in Java J2ME.

Gome is a J2ME go game application. It features online gaming, problem solving, game reviews and much more ...
Main Features
- Review commented games
- Play and record your games
- Solve problems
- Study joseki
- Evaluation of positions
- Play with another gome by bluetooth
- Access to an online updated go library of commented games and problems
- Local repository in which you can import online files to review/play them later
- Compatible with SGF file format.
- Available in English, French and Japanese.
- Play online on IGS
- Send your recorded games by email

Go Features
- 9x9 / 13x13 / 19x19 Goban
- Handicap stones
- Ko rule
- Optional joseki dictionary (for machines with enough memory)
- Counting feature
- Clock feature

Graphic features

- Show annotations on the goban
- Zoom
- An optimized size and collapsible scroller that show the comments