how do I give users capabilities

The original question asked how to grant users the capability to change file ownership. This is probably not a good idea, but you could grant a given user (or group) the ability to sudo and "limit" that to the chown command.

You might want to limit it further by installing (into an area where they could not modify it) a script which does the chown after checking that the pathnames it affects are not in the system area (though the recent security fixes for OSX would ward off most of the potential damage).

More generally, sudo is where to look. It can allow users (or groups, which means any user who's a member of a group) to execute specific commands — or any command.

Further reading:

• Allow An Unprivileged User To Run A Certain Command With Sudo
• Allow certain guests to execute certain commands