I'm still a n00b at setting up mods for myself, so sorry if I'm missing something really obvious. I was able to get it working with several other mods for 1.5.2 without a problem, but wanted to upgrade to 1.6+ mods. I first attempted the 'recommended' universal download for 1.6.4 (18.104.22.168) but BoP world type never showed up in my world creation menu. Realized this was incompatible with Alternate Terrain Generation (which was the main mod I wanted to test out along with BoP) so I changed to the development version 22.214.171.124. Still no BoP world type choice, and the biomes didn't show up in ATG world type generation either.
I've tried deleting config files and changing the versions again, removing ATG, putting it back in, reinstalling Forge altogether, but no matter what I do, BoP doesn't show up as an installed mod in the main game menu at all. As far as I can tell, all you're supposed to do is paste the .zip into the .minecraft/mods folder, and that has worked for all other mods. The other ones I have installed at the moment, which currently seem to be working, are: Thaumcraft, Forestry, Bibliocraft/Bibliowoods, Natura, NEI, Optifine, Twilight Forest. Thaumcraft biomes such as Tainted Land and Magic Forest are generating, as well as Thaumcraft structures and Natura stuff, in both ATG and default world types.
I've googled all permutations of this, read the BoP forum here and at the Forge forums, and I can't find anything about this sort of problem so I feel like it must be something incredibly stupid that I'm missing. I'm at my wit's end trying to get it to work, after successfully troubleshooting everything else.