I don't see myself as an expert either regarding those things.
But I would compare it with Windows and Ubuntu for example. Windows has its own bootloader so does Ubuntu and Co...
Windows loads ntldr -> ntdetect.com -> boot.ini and Ubuntu get it's stuff sorted by grub. Booting both systems with just one bootloader doesn't work. Win needs ntldr and Ubuntu needs grub...
So all you can do is to combine these two.
That means you have to have both bootloaders installed and then two possibilities.
First booting Win bootloader and then pointing to grub for starting ubuntu or second booting grub and have it point to ntldr to start windows.

For N900; Meego needs u-boot and multiboot manages maemo, nitdroid and the others.
That's it. And because u-boot isn't needed for maemo it's not integrated by default in any kernels.


Sorry for not being able to explain in a more detailed way.

Greetz,

J4ZZ