A libre, open-source implementation of Minecraft's NBT data format (both Java Edition's and Bedrock Edition's formats).
This implementation is not based off any other implementation (especially not Minecraft's own - that would be illegal!)
Instead, it's been written from scratch, with the only reference used being the wiki.vg page on the NBT format
(and a guy in the Bedrock OSS Discord server who I asked about root lists. Thanks, Huntondoom!).