... Riot doesn't make LoLReplay. Riot hates replays, and doesn't support them in any way, shape, or form.
If you want replays, you might be best off to use na.op.gg. Click the "Ingame Info", then click the Record function. What happens is that they spectate your game, then have a save the network traffic from spectating to their server. When you want to play the replay, League connects to their server and spectates the game.
The saved file is a .bat, which can't be run on a Mac, but most of that is used for convenience of not having the user specify their League directory. Once you understand the basics of it, you should be able to type up a version for your Mac, and maybe even write a little script to automate the conversion from .bat to .sh