(Here's this http://aminoapps.com/p/75vebb if you want pics. I keep doing this because I'm from amino.)
Disclaimer, this is just my opinion, so please don't hate me when I make this. Anyway let's get right to it.
Evidence 1: they both look the same! Okay so you might be thinking, why am I using this? Well, it's mainly because golden Freddy is basically a yellow classic Freddy fazbear. What is fredbear? He's ALSO a yellow classic Freddy fazbear! The only difference is that he has a purple hat and bow tie instead of the Normal black. BUT it can be explained that the colors have been rusted up a lot.
Evidence 2: nightmare fredbear and withered golden Freddy can turn into giant heads. This is ONE thing people ignored a lot, BUT since fredbear turns to a giant head, do you know it's like a reference to what's gonna happen 4 years later aka fnaf 2? I mean think about it, why else would Scott use nightmare fredbear to turn into a giant head just like golden Freddy from the second game?
Evidence 3: eye color. Uh.. this may sound dumb, but if you compare the minigame version of fredbear AND golden Freddy (fnaf 1.) In the thank you image, you'd notice a very very very identical brown eye color between the 2. I mean sure everyone can have brown eyes, but the only ones that I know that has brown is really only fredbear and thank you image fnaf 1 golden Freddy, and like I said, golden Freddy and fredbear have the same suit design.
Evidence 4: they both have the same fate. Why do I said that? Well remember how golden Freddy looked like he was scrapped for like... I don't know, a few years ago? Well guess who has the same fate? Fredbear! I mean fredbear literally is scrapped because he is the one who caused the bite of 83. Plus if golden Freddy wasn't fredbear, why is he scrapped? I mean they didn't explain why that's the case.
Evidence 5: stage 01, stage 01 HAS 2 golden suits that are named fredbear and spring bonnie, but that's NOT their names in the fnaf 3 game files, but their names are literally springtrap and GOLDEN FREDDY! I mean why does it matter? Because golden Freddy has a springlock bunny with him. Who else has the springlock bunny? Fredbear! I mean why else would Scott named them both golden Freddy and springtrap? Just to show that they are, in fact, spring bonnie and FREDBEAR!
Evidence 6, fnaf world. Yes I know, it's non canon, BUT they look the same, Why else would Scott use adventure fredbear for adventure golden Freddy? Like I said, to proov that he is in fact GOLDEN FREDDY. I mean they both share the same design, lack of kneecaps, and they both have the same color. The only difference is that he has a purple hat and bow tie instead of the Normal black and he has eyes, but like I said, it can be explained that fredbear was scrapped.
Evidence 7, the silver eyes. Fredbear is described as a yellow Freddy Fazbear, and who else is a yellow Freddy fazbear? GOLDEN FREDDY. I mean in this book, they actually said that golden Freddy is in fact springlock like fredbear, who is in fact GOLDEN FREDDY, they show that William uses fredbear in the books, who now has no eyes and his hat and bow tie are black instead of purple.
Evidence 8, bite of 83. Okay when you look at fnaf 1 golden Freddy and then you looked at his teeth and wondered WHY he has some kind of red lighting on his teeth, well after ucn and fnaf 4, it gives us an answer that in fact GOLDEN FREDDY is the fredbear that in fact caused the bite of 83. I mean gol den Freddy has blood on his teeth, and if think that's just the lighting, then why doesnt the same lighting go to fnaf 1 freddy? I mean when Freddy is on stage his teeth has some yellow lighting and when he is on night his teeth is white, HOWEVER with golden Freddy his teeth is white, BUT with part of some red lighting on the top of the teeth.
Evidence 9, the DARTH COIN. When golden Freddy appear in your office use the death coin on golden Freddy when his AI is set to number 1, you get fredbear as the jumpscare. If Scott wanted to make him different from golden Freddy, why the hell does golden Freddy have death coin mechanic to spawn fredbear instead of, ya know, NIGHTMARE FREDBEAR?! Also if he wanted them to be different then why do they have the same design?
Evidence 10 and final evidence, their plushie are the same, I mean why would they both have the same design when they are plushies? I mean if fredbear had a plush, you would imagine that the fredbear plush would have had a new design with the buttons, lack of eye brows and no ears right? Well you're now wrong, the golden Freddy and fredbear plush has the exact same design, with difference. Well maybe the jaw is different but other then that, no difference what so ever.
Anyway, that's all I have to say for now, hopefully you guys won't hate me on what I said, but I had a gum talk, anyways that's all, bye, have a good time.
Oh and sorry if I sound really cringy and rude, I'm just socially awkward.
Oh yeah and this is just my opinion, as I said earlier, i just think their the same because of one thing... I don't want springtrap to be the only fredbear's animatronic, it may sound idiotic but it's true. I just think it makes no sense that there would be another golden bear, plus why did the company even make him if he's gonna be scrapped anyway? Anyway I know this reason is kinda crappy but oh well, I tried..