Why can't I use this mod and the original Mining Drones at the same time?

This is a fork of the original Mining Drones, so the namespaces of all the prototypes would collide and Factorio would refuse to launch.

When would I want to use this version of Mining Drones over the original version?

Currently, the only time you would want to use this version is if you also have the Factorio and Conquer: Tiberian Dawn mod active (https://mods.factorio.com/mod/Factorio-Tiberium). This mod adds an interface feature that lets mining drones mine Tiberium Ore as it spreads.

What if I have an bug/suggestion for Mining Drones that is unrelated to Tiberium, can you fix it?

Probably not, but you can ask Klonan about it on the original Mining Drones discussion page https://mods.factorio.com/mod/Mining_Drones/discussion