Well, it depends. Mainly GPLv2/v3 or BSD-style. The vast majority of the system is designed for dodging the GNU userspace with a few exceptions, every source package will be available in the repo so you can figure it out.
Personal use or development. The bootstrap image is just supposed to feature a toolchain, package manager, init system and basic userspace tools. A bunch of binary packages will be hosted on the online repository, but things like an X11 environment will have to be built on your end using pkgsrc.
There's the POSIX sh-based custom `pkgmgr` (basically just a set of scripts to update the base system) and then there's `pkgsrc` (source) with `pkgin` (binary).
Most answers you can find in manpages of the packages or the pkgsrc wiki pages, and there's a plan of creating a documentation page for the `pkgmgr` package system on the repository tree.
Yes! Please try to avoid using GNU utilites as much as possible, use filesystems like btrfs, JFS or HFS+ (to replicate my experiences) and use LTS kernels.
Possibly in the future, but as for now I'd prefer to have people building their own images simply because of how god damn heavy my personal config is, heh...