GPT partitioning can be done using a "protective MBR" partition, that's meant to preserve compatibility with system who don't understand GPT partitioning (very few these days).
MBR based partitioning is still desirable at least for one use case:
when an MBR setup already exists (say using a Linux install) and the user would like to dual boot adding GhostBSD.
Facts are that not all Linuxes can easily coexists with GhostBSD/FreeBSD, several do not understand BSD partitioning like 'slices' which must be enabled in Linux kernel to work, and that make difficult read/write UFS partitions.
The other way around, only ext2fs is supported R/W from GhostBSD/FreeBSD which is rarely used these days in Linux, and that also add difficult to coexistence of both system.
Basically, from a final user perspective, a dual boot install is not going to work as expected.
ZFS should be a better option for dual boot systems, but Linux is late on ZFS support, so it is a choice reserved to somewhat advanced users.
Considering all the above, I'm not sure an MBR setup is really needed/desirable, I would drop it in favour of a more reliable support of GPT.
should we drop MBR based setup ?
Re: should we drop MBR based setup ?
I have already answer you, but I thought I should answer here, just to make sure that everyone who can read here knows what going on. Like said I need MBR and I have some plan to make it better and limit the use if it can damage other partition.