When comparing the image above to the original comic, we can see that...
the text "DRM-free files" at the bottom right is replaced by "0XAmp" (a zero, not an O). Using this instead of "kLvQR" for the post image link leads us to this new image, which has five letters that differ from the original comic:
The letters "KRODF" become "WVNZ2". The correct order is "V2ZNW", with the characters ordered based on their position in their respective text blocks ("W" is the fifth character, "V" is the first character, etc.). Using this in the image link leads to a new image:
If we replace each number
5 8 -5 13 42with the character at that position in each text block, not counting spaces or non-alphanumeric characters, and assuming negative means counting starting at the end and making it lowercase, then we get "KRiR0". Using this in the image link leads to a new image:
On the surface, this doesn't appear to differ from the original comic, but if you adjust the intensity you can see some ghosted text appear. I processed the image in MATLAB using the code
imwrite(uint8(255.*(imread('KRiR0.png') > 245)), 'adjusted.png');to get this:
And the characters "EdxNK" (read from top to bottom) appear. Using this in the image link leads to a new image with 5 changed letters (4 lower-cased and one removed):
And finally, using "goioF" in the image link leads to the final image:
Phew! All that image stealing made me tired! Thanks to everyone who was solving it alongside me!
Joe-You-Know spotted the key difference between the image in the OP and the original XKCD comic:
the replacement of "DRM-free files" by "0XAMP", with the MP smaller than the 0XA.
looking at https://i.stack.imgur.com/0XAmp.png - where we find:
In this new image, we can again spot the key differences from the original XKCD comic:
the letters K, R, O, D, F at various points have been replaced by W, V, N, ?, 2. I'm not sure what that fourth character is - R? Z? - or which of these are supposed to be lower-case, but presumably these letters will lead us to the next image.
After following a series of clues and finding the differences of the last one, you end up with
As the final picture. (I'll update my answer to reflect this)
From the work gnovice has been doing.
Okay, I'm not sure if this is just spot the difference but here it is
In the original XKCD, the bottom line read "(If you don't like this, demand DRM-Free files)"
In this puzzle, it instead reads, "(If you don't like this, demand OXAmp), which is as far as I can tell is an anti-bacterial"
I feel there is more to this puzzle than just this difference, hopefully this will help others though.
you get this image:
This shows some numbers. If you add them to the letter positions I get this:
k(11) + 5 = p(16)
r(18) + 8 = z(26)
o(15) + 13 = 28 = b(2)
d(4) - 5 = -1 = y(25)
f(6) + 42 = 48 = v(22)
pzbyv. Not sure what I can do with this ...
If you rot13 this you get
comli, maybe a misspelled comic?