The Mac Beta was a closed Beta and even though the link was posted more than once each time it was posted the thread was closed quickly and the person responsible for it was removed. The Mac Beta was closed mid september.
Originally Posted by Tamat
Last week we announced the imminent closure of the Mac beta for League of Legends after months of searching for a solution that would allow us to release on the Mac with a service comparable to what we offer existing PC users. We’ve been reading your feedback and understand your concerns. We’d like to clarify two aspects of our announcement which have been at the core of most player feedback and questions:
RP Refund Program
In the coming weeks we will be sending out an email to those who have purchased RP within the Mac client with instructions on how you can get the money used to purchase RP refunded in exchange for removing all items purchased with RP and any remaining RP balance that came from an RP purchase. Additionally, we will not be closing the account you played on! It’s your account after all, leveled with the determination of hours on Summoner’s Rift, so it’s yours to keep. We’re already hard at work on a new Mac client and though it will take some time to complete, we want to make sure that Mac users can return to their accounts when we’re ready to begin Mac testing once again.
Champions Bundle Reward for Mac Beta Testers
All players who had a majority of their logins through the Mac client will automatically have the Champions Bundle added into their accounts in the coming weeks. Players who did not get a chance to login to the Mac Client and click on the store button in the week leading up to September 6 need not worry, as our intention is to provide this reward to all players who actively helped us during the beta test period.
We know how many of you want to enjoy League of Legends on the Mac, and we’re determined to make that possible long term. Thanks for your patience as we reinvent our Mac client.