Pro Git book describes the difference between those names as follows: the author is the person who originally wrote the work, whereas the committer is the person who last applied the work. So, if you send in a patch to a project and one of the core members applies the patch, both of you get credit – you as the author, and the core member as the committer.
SubGit translates Git Up to the version 3.3.4 SubGit only used Git author name, so committer name doesn't mean much for the SVN-to-Git translation processso committer name did not mean much.
Since v.3.3.4 SubGit uses committer name for the author mapping by default. Since v.3.3.6 there's also an option to switch back to using author name for the mapping with the core.mapGitCommitter setting:
[core] mapGitCommitter = true|false
When it’s set to true (default), SubGit uses committer's name. Set it to false to make SubGit use author's name.
Note, that SubGit uses authors names to count licensed users, see Licensing manual for details.