For those of you saying that you got into the alpha but can't login to the beta... it would be helpful to read the full message before saying it's a scam...
"
Please note: the Interface System Alpha is separate to the HTML5 Client Beta.
If you've been selected for that, you will already have received notification"
Seeing as this message came from the runescape link that was in my contacts list, I can confirm for myself that this particular message is legit. It's also worth noting that if it doesn't force you to use a link, and it shows your username, then it's probably legit, as well.
23-Apr-2013 23:58:49