Uhhh, dude. Apple doesn't make RAM. Or hard drives. They buy the same memory (read: third-party ram) that anyone else does, mark it up 300%, then stick it in there for you. I've taken many computers in for service with "third-party parts" - that is, ram, hard drives, etc. that I've installed by myself that were not repurchased from apple - and I've had no problem. That's because apple has NO WAY to tell if your parts were installed by a certified technician or not.
Common sense should also apply - most of the computers that ship new from apple have instructions in the manual about how to upgrade the RAM. Nowhere do they tell you that doing so will void your warranty, quite simply because it will not.
Short version: There is no such thing as non third-party RAM, because Apple doesn't make RAM.