The following tables compare general and technical information for a number of available bootloaders.
Official website
Source repository
Note: The column MBR (Master Boot Record) refers to whether or not the boot loader can be stored in the first sector of a mass storage device. The column VBR (Volume Boot Record) refers to the ability of the boot loader to be stored in the first sector of any partition on a mass storage device.
Since we have copied the Linux kernel code and the Linux kernel follows GPL2, so only GPL2 is adoptable and it rules here.
If you enabled the network support, the special drives (protocol[,server]) are also available. Supported protocols are 'http' and 'tftp'.
Since 10.3-RELEASE, the BTX loader included in distribution supports Multiboot, but only for Xen (the Xen image is a Multiboot-compliant kernel). ... Because this multiboot support in BTX loader is designed for Xen only, it requires the first Multiboot module be original kFreeBSD image. Trying to load a Multiboot kernel without loading any Multiboot modules would resulted in BTX loader complaining 'No FreeBSD kernel provided, aborting'.