Yes it's possible. I have been using GPT disks on machines that only have legacy BIOS without any problems.
1 efi (256M) 2 freebsd-boot (512K) 3 freebsd-swap (8G) 4 freebsd-zfs (remainder)
You will need a GPT partition of type freebsd-boot that holds either /boot/gptboot or /boot/gptzfsboot depending on whether you will be using UFS or ZFS for your root partition to boot from.
UEFI is not a requirement to be able to use GPT. Most older BIOS booting machines will be able to deal with GPT thanks to the way the PMBR works. That said, some really old machines can have difficulty with it though, they usually don't like the "fake" MBR partition that GPT creates. Whether or not GPT will work really depends on how "old" that machine actually is.a GPT disk but on a server whose firmware is not UEFI
The installer allows you to choose between GPT-CSM, GPT-UEFI or a combination GPT-CSM+UEFI. The combination creates both freebsd-boot and efi partitions allowing you to switch back and forth between UEFI and CSM boot.It's probably a good idea to also create a GPT partition of type efi as the first partition on the disk, even though a BIOS system will not make use of it, but it saves you the hassle should you later upgrade to a UEFI capable mainboard.
Different issue. The original question basically wanted to CSM boot the machine and use UEFI features. That's not possible, it's one or the other, not both. It had nothing to do with GPT.