Alright, looks like I was wrong. I must've opened the wrong output.dat somehow (apologies to the OP) as that download definitely isn't YSMenu.
I've just run this in a file compare util though and there are 510 bytes at the very end that is different. If you unpack the decrypted files all the unpacked files match byte for byte so I'm unsure of what the difference in data is or does. It's definitely a hacked version of 1.18, what the hack is though I don't know.
The original poster claimed he created this, then he claimed he didn't know what was done, then he claimed he got it from a friend. It still smells pretty fishy to me but I will admit that I made a mistake in my first assessment of it being YSMenu. Using file names and structure isn't enough to guarantee it's not YSMenu though, the fake R4 Team released 1.19 which looked completely different file structure wise to Yasus firmware but opening it up in a hex editor showed the YSMenu strings at the end, which is why I checked this one in the file editor.
Again, my apologies to the OP. Although I'd like to know where his friend sourced this from so I can find out what's been done and why it allegedly works. I don't think any veterans here will give it the ok until then, but anyone who wants to try it out should but at their own risk.