Mac play not added to path
Just add path to the play installation to your .bash_profile file in the user root directory. 

For example I have 

export PATH="/usr/local/mysql/bin:/Users/currentuser/PlayProjects/activator:$PATH"


This discussion could help you as well:

https://superuser.com/questions/314852/how-to-install-the-play-framework-on-os-x