Minecraft is still copyrighted material, they run it through an obfuscator before publishing it as a minimum level of protection.
As far as I know, these are the naming schemes that Minecraft can exist in:
Mojang Names
Obfuscated / Proguard Names
SRG Names
MCP Names
...and this is how the process goes:
Mojang develops the game using human-readable names
Mojang publishes a version of minecraft that is built and obfuscated (I'm not sure of the order at this stage).
The MCP/Forge team decompile Minecraft and run it through a toolset that analyzes the code and remaps it to a new set of names while trying to identify previously known classes, methods, and fields and label them with the same names they had in previous versions.
During ForgeDev and ModDev, ForgeGradle remaps these names again to Community-Contributed Human-Readable names
During Forge and Mod publishing, these names are mapped back to the intermediate mappings to keep them consistent at runtime
If a member of the core team wants to correct me, please do so I can update, refine, and possibly reuse this explanation