This may be a dumb question, but what is Rosetta Beta? How does it differ from normal Rosetta?

After a long dearth of Rosetta tasks, my computer has been running Rosetta Beta 6.04 with no problems.

But I don't know what it is.

Why the switch to Rosetta Beta 6.04?

Did they run out of standard Rosetta tasks?

Thanks.
S. Gaber