@toMAcash
I must let my more learned friend, chscag, speak for himself. But my understanding had always been that if you owned (ie purchased) an OS where iPhoto was an included app, then you could re-download iPhoto for free at a future date. This is definitely and unequivocally true if you upgrade from one OS to another (SL to Yosemite in your case). But I did just wonder if you bought a new Mac with Yosemite pre-installed, whether that remained the case. It seemed logical that it should , but I raised the question anyway and chscag (Charlie) confirmed that this was so in his experience.
In your case, come the day when you either upgrade to Yosemite (or whatever is current at the time); or whether you buy a new Mac, then the fact that you previously owned iPhoto as part of SL, means that you can still get the latest version of iPhoto for free by going to the App Store and clicking on the purchases tab.
Ian
EDIT: as long as iPhotos is still being supported at the time.