There's no special "bootstrap compiler"; you can download a binary release for your platform from the page you linked, and then use that to bootstrap a newer version from a source checkout. If it would help, we could provide a minimalistic build that was only useful for bootstrapping, but at present our builds are "batteries included" (with LLVM/Clang and the BDW garbage collector already provided in the tarball).
So for Dylan, we'd like to have a compiler for Open Dylan, not written in Dylan. (it can also require multiple steps to get up to Open Dylan--that would be fine)
It's not in the interest of our users to use binary blob compilers for bootstrapping.
We would also unbundle LLVM, clang and the bdw gc and use the ones from Guix.
