Grouper API javadoc is here:

Grouper 2.3: https://cdn.rawgit.com/Internet2/grouper/GROUPER_2_3_BRANCH/grouper/doc/api/

This is updated by running the "javadocFoSvn" ant task in the api, sync, and commit

Note, you can change: GROUPER_2_3_BRANCH with the branch to look at, though 2.3 is up to date as of 6/23/2017