for those of you without the patience to read a blogpost, the new name's actually a bit of wordplay.
“Luanti” is a wordplay on the Finnish word luonti (“creation”) and the programming language Minetest Luanti employs for games and mods, Lua. The goal was to avoid yet another plain English word (good luck finding something unique…) and highlight the core principles of the project. The fusion of celeron55’s Finnish nationality and the platform’s focus on content creation resulted in the birth of “Luanti”.
IMO, the worst thing about "Minetest" is that it sounded like it was just a test creation, a prototype or experiment. It's certainly well beyond that now. The announcement introduction mentions people associate it with being a Minecraft clone or alpha release, but even further, to me the name initially gave me the impression it was [still] someone's small hobby project. 'Luanti' is much better.
On this note, another thing I appreciate is what they said about "Free" and "Libre": those names are great for saying "This is a free/libre/open clone of [x]", and that's what I'll think when I see it. Software like LibreOffice aims to support Microsoft Office documents, OpenRTC2 and OpenTTD are for people who want to see those games pretty-faithfully cloned, even if extended. Luanti is not OpenMinecraft.