Grub4dos, meaning grub for dos, comes in two flavours:
1) grldr <- an executable that can be chainloaded directly from BIOS through a bootsector, like *all* bootloaders/bootmanagers and from some special code in the MBR (+hidden sectors), like *most* bootloaders/bootmanagers but - unlike most other bootloaders/bootmanagers - also chainloaded from NTLDR and BOOTMGR and usable also as no-emulation bootsector on CD's and DVD's .
2) grub.exe <- an executable that can be run from Dos command line, unlike most if not all bootloaders/bootmanagers (BTW grub.exe is also a Linux executable and can be loaded from kexec and lilo)
I guess it is enough to understand the basic reasons for the name.
Read the "Introduction" here for a few more details (in the long years since this grub4dos has been considerably extended with - among many other things - an extremely useful script language and very powerful internal commands, such as write and dd):
It is intended - just like GRUB (the real thing, now senselessly renamed GRUB Legacy) for BIOS, that's it.
It is entirely possible that - before or later - it will be extended to make use of UEFI besides BIOS, though nowadays there is no real *need* for this.
The new thing for UEFI, the GRUB2 (now senselessly renamed GRUB) is completely different from (it is a rewrite) the original GRUB, it took YEARS to be developed to something actually - somehow - working, whilst the GRUB (the real one) was left in a 0.97 version (and had all in all a very limited usability/flexibility).
The guys who rewrote it clearly had/have different ideas from the ones that wrote the original one and introduced (besides UEFI support) a number of (largely unneeded) complications, managing to make it more complex, both in the structure and in the way it is managed.
To put the above in context, read this (2009) article by dedoimedo on GRUB2:
and the corresponding one for GRUB:
and consider how grub4dos became largely popular around that time ....
And yes, grub4dos is MUCH more "flexible" than any other bootloader/bootmanager.