Learn more about these different git repos.
It looks like being able to use lzma (actually xz) is going to be possible for this release. I have a concern about making the versions of livecd-creator squashfs-tools that supports this available on whatever system is used to build the official spins. Currently the support for this is going to be just for F15. squashfs-tools 4.2 is needed for the proper support. I'd rather not do that update on F14 or F13.
Also xz compression doesn't get made the default for livecd-creator in F15 or the F14 version of livecd-creator is used (with an updated squashfs-tools), the compression type will need to be specified when doing the build. Which is different than what has been done in the past.
This looks good to go now wrt f15
to comment on this ticket.