I am using a starter license, and while trying to get the total committers down to 10, I used the suggested approach of starting from a later revision:
Set a starting point
Some of the FishEye SCM integrations allow you to configure a starting revision from which to start indexing. All commits prior to this starting point are not included in FishEye and do not contribute to the committer count. Read more.
However, if you do this and choose to initially import the state of the repository prior to that revision, FishEye will create an anonymous user that ends up counting against the 10 committer limit, so actually you only get to have 9 committers. I think this is a bit unfair, as the whole idea was to skip over commits made by other users, yet we get penalized by then only getting 9 committer slots instead of 10. And if you don't choose to do an initial import, you lose access to any files within the repository that were never touched by anyone after that revision, which should not be part of the restriction as the license currently reads.
FYI, this is using a subversion repository.