Everything is up at https://github.com/lowrisc. We recently had a website redesign which is 'soft launched' (in that there are a number of regressions like this I need to sort out). Amongst other pieces of IP, we build upon the Rocket implementation from UC Berkeley, which has a BSD license, as well as the PULPino implementation from ETH Zurich (which has an Apache-style license).

So is BOOM officially not going to be the core for the first run, then? If so, are there plans for later generations to switch to it?

Assuming sufficient die area on a 28nm test chip, we would like to have a heterogeneous cluster with something like 2xBOOM and 2xRocket.

Can you please add a link to that from your website?

I've added a link on the 'about' page, in addition to the link that was already there on 'community'. A future restructuring will make it more prominent in the top-level navigation.