These lines in the FAQ of Biomes O' Plenty may be the reason:Was hoping to see Biomes o Plenty to be added but glad were one step closer to a final version
Don't know if there will be an aggrement about that later...Q: Can I add this mod to a mod pack?
A: No. This goes for any modpack, including Tekkit, Feed The Beast, and other modpacks.
First, find the FTB folder - you'll see the mod packs you've already downloaded (say Ultimate, TechWorld, etc....) - You should see 152ngt (in your case).For me the launcher is downloading and launching vanilla, regardless of auto setting or versions etc. I don't know where to find the 152ngt zip though, any help please?
Mind linking the source? Not sure if they've changed the FAQ in the time since you posted this but it now reads:
http://www.minecraftforum.net/topic/1495041-152-forge-biomes-o-plenty-v055-biome-specific-gemstones/Q: Can I add this mod to a mod pack?
A: Yes, as long as you give proper credit (Linking back to this thread, etc.), and don't make any money off of it (Adf.ly, etc.). You don't have to get explicit permission from us either, just follow those two rules.
It comes from the official wiki: (maybe not so official as I can't find any link to it on the page you posted)Mind linking the source? Not sure if they've changed the FAQ in the time since you posted this but it now reads:
Read the page 49 of this thread...Any tips?