Mac Retail version
The beta client for Mac just allows the account to login from a Mac. It has nothing to do with discs. If you own the game you can login from any computer, Mac or windows. The retail disc only contains a windows client, if you buy the retail disc, all you need to do it register an account and download the Mac client after registering the serial number.
https://buy.guildwars2.com/en/
Your friend can purchase the game at the above link. Both versions are included in the cost. Just make sure they register with a valid email address and a unique password. They can download either client from here:
https://account.guildwars2.com/login
The game functions the same whether it is pc or mac, just as long as they purchase the game, they should have no problems getting the Mac verdion for themselves. If they already downloaded the client, they just need to log in with their own newly created login. Easy easy! No discs ever required, just 20some Gb of downloads ;p
I bought mine from Amazon (digital download). I ignored their Windows download, grabbed the account key from their email, and downloaded the Mac client directly from ArenaNet.
(And downloaded and downloaded and downloaded…it’s not a small download…)
Purchasing the account is all well and good I am just hoping that if a Mac retail version comes out, the beta users can simply upgrade without having to purchase the proper version and having to pay a second time so they can use the optimized version rather than the functional (but not ideal according to Anet) version of the Mac game.
Thankyou guys for the links and quick responses, now just hoping for some form of confirmation from the team that people who play the Mac version but purchased accounts will be able to simply upgrade. I dont see why it wouldnt work that way as a download is useless without an account (which would’ve been bought already) but there you are. Friend and I just wanna be reassured 
You are probably violating some terms of use by letting your friend use your account.
Anyways, a game account exists independent of the client in use. Unless Anet discontinues the Mac client any account will be playable on the Mac, whether it’s beta or final version.
The concept of a physical copy of a game has died a long time ago (although retail boxes still exist).
Yep, one purchase is all it takes. You will never be charged extra or have to buy another account whenever the Mac client is out of beta… So have your friend buy their own account so you don’t have any issues
Oh lame I hope not Lilsteele, I figured so long as I purchased the account, I can let anyone have a go on my characters if I so choose. I mean I own the account I paid for so who I let try things out on should be my right and I dont own more than one, nor do they tecnically get to make anything on Guild Wars. No different t handing over a controller for a bit and just seeing how it runs on a Mac.
Oh well it won’t be an issue for long but thanks for pointing out the possibility I’ll have to check the User agreement in the mean time.
Oh lame I hope not Lilsteele, I figured so long as I purchased the account, I can let anyone have a go on my characters if I so choose. I mean I own the account I paid for so who I let try things out on should be my right and I dont own more than one, nor do they tecnically get to make anything on Guild Wars. No different t handing over a controller for a bit and just seeing how it runs on a Mac.
Oh well it won’t be an issue for long but thanks for pointing out the possibility I’ll have to check the User agreement in the mean time.
Sharing an account is the same as sharing music, or movies, illegally. You do not own your copy of the game, you’ve purchased the right to use it, your rights with what you can do with your right to use the game are clearly outlined in the ToS and/or AUP.