It was restricted to level 50 Global Agenda users but they need more to pad the roster. It's focused on the game's "huge battles on huge landscapes".
The Tribes IP is now owned by Hi-Rez Studios and Tribes Universe is their way of moving the long-time multiplayer FPS franchise forward by making it into a MMOFPS.
"Because the game will be focused around huge battles on huge landscapes, we need a solid group of very dedicated testers that can help us from the game's earliest stages to validate the scalability and performance of the game, while also helping tune and refine gameplay," said executive producer Stewart Chisam.
If alpha testing and Tribes is your thing thenfor a tour of duty. Level 50 Global Agenda users are given priority to alpha and beta testing for Tribes Universe.