The distinctions used to be somewhat clearer but recently Minecraft has been scrambling to add all kinds of last minute role playing elements.
Ultimately, the difference will be down to that Minecraft is at its core a mining and crafting game... where the crafting tree is extremely specific.
Mythruna is a role playing game that will take advantage of the flexibility of a block world to _allow_ mining or crafting but really that's not the focus. If I reach my goals, players can have fun without ever mining a single block or without building a single thing. Those things will be available to them if they want but that's more of a side effect of the engine choice and because it would be mean not to allow it given that I could.
When I started trying to write my own RPG many years ago, I wanted something that was visually beautiful, randomly generated, and that the world could be modified. Originally this was because I wanted rivers to carve through the world and because I wanted NPCs to be able to build houses, fences, etc... and to ultimately let the players do similar. If a bomb went off in a castle then the castle should blow up and so on. Down that path, I started trying to make an engine more like Oblivion. My terrain generation was all geared towards realistic terrain, etc.. The problem was that I was spending all of my time trying to allow things like roads and rivers to be added and there are issues trying to combine height-map style terrain with fixed structures while still being flexible. I had several failed attempts that never made it to anything usable.
Fast forward to many years later and I played Minecraft. It struck me that a block world was simple enough to write that I could get it done pretty quickly and have almost all of my original requirements met. And I hoped that I could tweak it into something that could still be visually stunning. Within two weeks, I had the basic engine done and could start on the rest of the game elements. The rest has taken me much longer than I had hoped... but it moves forward.
Do not harshly judge the current version. Right now the game is just a test engine. In order to test things, I give the players infinite resources and let them place whatever blocks anywhere they want because it really works the heck out of the engine. And I will always try to support this mode as a nerfed version of the game because it's fun and some players will like that better than role playing.
But the real game will be more. There will be real monsters to fight, gold to earn, rare materials or magic items to collect, NPCs to build relationships that will ultimately help your place in the world. If I reach all of my goals, there will be no fixed crafting tree. Items will be whatever you make and will behave like they should. You can see the beginnings of this with the current object builder but I have designed much more for the usable items. (Some of which may be impossible but I hope I can make it work.)
You can see some of where the custom objects are going here:
http://www.youtube.com/watch?v=rX-MOerwQSkThere will also be sailing ships, air ships, etc. that the players can build themselves or just ride on the ones run by NPCs. And if you imagine being able to link things together with hinges, ropes, and pulleys, you start to see some flexibility for creation of just about anything. I'd like every object, item, weapon, armor, clothing, etc. to be buildable in-game.
I also pull a lot of influence from the Neverwinter Nights community. That was a great game on its own but had an extensive modding community. There were servers you could log into for basically any style of role playing you wanted to do. There was even a Lord of the Rings mod that was nearly a total customization. I want to support modding out of the box so that modders can add their own creatures, building types, quests, items, etc.. Maybe someday I will be able to login to someone else's Mythruna Lord of the Rings server.
In conclusion, I'm trying to make an extensible role playing game that just happens to be in a block world (and I will happily drop the block part if I ever figure out how). I'm not trying to make a mining/crafting game with some role playing elements. There are already games like that.
