Brown nosing and gaining Brownie points are DEFINITELY NOT related.

Brownies are a division of the Girl Guides for younger ladies. When you learn to master a specific task you get points and badges. For the Brownies (6 and 7 year olds) the tasks are relatively simple...learning how to make a simple breakfast, arts & crafts and the likes. The term Brownie points came to mean accumulating points for doing good things and is a positive expression.

Brown nosing on the other hand is a negative expression. It is related to that common expressing - kissing the boss' ass. Publicly agreeing with everything he's says weather he right or wrong, fawning over him, etc… When you are brown nosing you are kissing it so close that, well, you get the picture.