I get this warning at:
/Minecraft/src/biomesoplenty/blocks/BlockBOPGrass in line 86:

if (blockID == blockID && side == UP)
return true;

Little fix:
int var1blockID = 0;
if (var1blockID == blockID && side == UP)
return true;

Hope that helps. :)

You do realise, by leaving nothing before blockID it is the same as this.blockID. Otherwise, the game wouldn't compile and we would have fixed it ages ago.

hmm... but it works for me and it compiles without errors :)