Lore: Loremasters gather knowledge. At second level, a loremaster gains the ability to know legends or information regarding various topics, just as a bard can with bardic knowledge. The loremaster adds her level and her Intelligence modifier to the lore check. See page 28 of the Player's Handbook for more information on bardic knowledge.
Bardic Knowledge: A bard picks up a lot of stray knowledge while wandering the land and learning stories from other bards. He may make a special bardic knowledge check with a bonus equal to his bard level + his Intelligence modifier to see whether he knows some relevant information about local notable people, legendary items, or noteworthy places. (If the bard has 5 or more ranks in Knowledge (history), he gains a +2 bonus on this check.) A successful bardic knowledge check will not reveal the powers of a magic item but may give a hint as to its general function. A bard may not take 10 or take 20 on this check; this sort of knowledge is essentially random. The DM can determine the Difficulty Class of the check by referring to the table above.
So with Bardic Knowledge u can take a knowledge check on every knowledge there exists?I have quoted the appropriate sections of the PHB and DMG.
Okay so, as I understand it, Loremaster's levels stack with the bard but otherwise works exactly like bardic knowledge. So take Loremaster + INT mod then roll.
I know it's a bit ambiguous but based on other examples, it should only count loremaster levels not ALL HD.
In case anyone else out there needed the references, there they are in case you want to dispute my answer.
so its up to the GM when bardic knowledge can be used?
so its up to the GM when bardic knowledge can be used?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.