The 0.5.0 version of Apparticle for Mac was available to download on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. This free Mac application is a product of PjEr.ca. We recommend checking the downloaded files with any free antivirus.
From the developer:
Apparticle is an open source GPLv3 Mac software program that lets you edit particle systems and save them in the .plist format to be used in a Cocos2d-based project. This project was created in an academic context with the need for a cheep, simple, but complete particle editor for Cocos2D.