Here's what the FAQ at dndnext says:
"Am I allowed to make copies of the playtest materials or publish parts of them on my blog?
As part of your participation in the D&D Next playtest, you must agree to our playtesting terms and the Online Playtest Agreement, which prohibits copying, excerpting, redistributing and the misuse of playtest materials. (This does not limit participants from making copies of playtest documents for the sole purpose of sharing them with their gaming group provided they have all signed up to playtest D&D Next.) For more information, see the Online Playtest Agreement."
Note the parenthetical. If your entire group is signed up, and you simply missed the latest download, you can get it from someone else in your group who knows you are signed up.
Since you can't sign up anymore, if you aren't signed up you are out of luck. This also unfortunately seems to apply to bringing new people into your group.
I will note one fuzzy area. If you watch any of the livestream games (which you can still legitimately access online) they will say that by watching them you are agreeing to the online playtest agreement. So it is still possible to agree to the online playtesting agreement. It isn't, however, still possible to sign up for the playtest. A strict reading would disallow sharing materials with someone who has agreed to the playtest agreement but not signed up. I think it's absolutely absurd, and my Lawful side would be at war with my Chaotic side as to whether I felt justified letting a friend who had legitimately agreed to the playtest agreement, but was unable to sign up due to the option being removed, join my group, but there you have the official details.
