Spongebob sailor mouth uncensored audio

It seems that they instead improvised fake words that they then dubbed over with dolphin sounds.

I am pretty sure that no uncensored audio for this episode exists. I am guessing that the cast had to make up fake swear words so the crew can put dolphin noises on top of their dialogue and no child could figure out what swear word they actually said.

Even if it did exist, how it's censored is part of the joke of the episode. It was clearly conceived to be "censored" from the beginning and is intended to be that way.

so the youtube uncensored version was fake because putting swearing words on diffrent audio from videos.

Tom Kenny has Sworn in Character before, But I haven't heard the rest of the crew swear before

I'm pretty sure that the "I'm Mad" swearing claim has no ground in reality and is likely just a joke/prank/hoax edit. People just love to make interpretations of the fake swear words (albeit censored with dolphin noises) the characters were saying.

Otherwise, I believe what you have said is true about Tom Kenny (the voice of SpongeBob) saying that the swear words were made-up on the spot on the episode's description in iTunes.

Here is the episode's description that Tom Kenny gave on iTunes (you can find it at #16 on "SpongeBob SquarePants: Tom Kenny's Top 20" episode list if you search for "SpongeBob" under TV shows):

"This was also one of the silliest recording sessions ever. We had to come up with fake "cuss words" to stick in the dialogue to be "bleeped out" later. I was laughing so hard, they recorded me while I lay on the floor of the sound booth."

Sounds like a fun voice recording session to be in. 

There was swearing during the recording sessions of the first episode of Freakazoid!, for the scene where Freakazoid rants at Jeepers (which was totally improvized), but the engineers apparently turned off the microphone as soon as it started, so audio wouldn't exist.

EDIT: Apologies, Craig McCracken said that "Rude Removal" was indeed recorded using real curse words, but denies knowledge of that audio ever being synced to animation.