Nutrient content of ground bison meat
None of them are right—or, all of them are right.

"Ground bison" does not fully describe the product. Any ground meat is produced from one or more cuts of varying fat content, and usually does not have the same overall fat content as the average across all cuts of meat for that animal. So, to have a chance at comparing these different sources of information, you would at least need to know the fat content of the ground bison meat. To make things more complicated, the %fat indicated on ground meat labels in the US refers to the maximum proportion of fat in the product from a regulatory standpoint. There is some flexibility in how accurate the label must be for the product to be in compliance with federal regulations, so the actual fat content could be as much as 20% more or less than the advertised value; but in practice, a vendor won't get in trouble for selling meat that is leaner than advertised (even though this would be very annoying for those of us who are more concerned with preparing the dish properly than having it be low-fat). From the USDA Food Safety and Inspection Service guidebook:


  Q. Is the leeway on values still 20 percent?
  
  A. Yes. The regulations in 9 CFR 317.309(h) and 381.409(h) specify
  that certain nutrient values are not out of compliance, unless they
  are more than 20 percent above the labeled value. That rule applies to
  the labeled values for calories, sugars, total fat, saturated fat,
  cholesterol, or sodium. These regulations also specify that certain
  nutrient values are not out of compliance unless they are 20 percent
  below the labeled value. That rule applies to the labeled values for
  vitamins, minerals, protein, total carbohydrates, dietary fiber, other
  carbohydrates, polyunsaturated or monounsaturated fat, or potassium.
  
  Q. If a producer is not sure of the lean and fat percentage of a
  ground or chopped product, could the producer label it with a worse
  lean and fat percentage? For example, could a producer label a product
  that is actually 80% lean and 20% fat, with a 70% lean/30% fat label?
  
  A. FSIS would not take action against producers estimating that their
  products are higher in fat than they actually are.


For an analytical perspective, check out this item from the Agricultural Research Service, which shows that at the lean end the of the spectrum, ground beef products are more likely to be fattier than the label advertises, while the reverse is true at the fatty end of the spectrum (near 70% lean/30% fat, which is the absolute maximum fat content allowed by law).

The other glaring problem with comparing these different sources of information is that the BisonCentral page is giving information for cooked meat, while the self.com page is giving information for raw meat. The sfgate.com page doesn't even specify cooked or raw so I would consider it the least credible of the three.

The nutritional information source I recommend is the USDA National Nutrient Database, which has over a dozen entries for various forms of bison meat:

NDB No.    Description
17148   Bison, ground, grass-fed, cooked
17149   Bison, ground, grass-fed, raw
17156   Game meat, bison, separable lean only, raw
17330   Game meat , bison, ground, raw
17157   Game meat, bison, separable lean only, cooked, roasted
17331   Game meat, bison, ground, cooked, pan-broiled
17267   Game meat, bison, top sirloin, separable lean only, trimmed to 0" fat, raw
17268   Game meat, bison, ribeye, separable lean only, trimmed to 0" fat, raw
17269   Game meat, bison, shoulder clod, separable lean only, trimmed to 0" fat, raw
17332   Game meat , bison, top sirloin, separable lean only, 1" steak, cooked, broiled
17335   Game meat, bison, ribeye, separable lean only, 1" steak, cooked, broiled
17336   Game meat, bison, top round, separable lean only, 1" steak, cooked, broiled
17337   Game meat, bison, top round, separable lean only, 1" steak, raw
17333   Game meat, bison, chuck, shoulder clod, separable lean only, 3-5 lb roast, cooked, braised
17334   Game meat, bison, chuck, shoulder clod, separable lean only, 3-5 lb roast, raw


In fact, if you look closely at the chart on the BisonCentral page, you'll see at the bottom:


  Bison, separable lean only, cooked, roasted. USDA NDB No. 17157


The corresponding NDB page doesn't agree exactly with the BisonCentral source (if you add up the lipid entries, you don't get 2.4%) but it's at least in the ballpark.

You have another problem: That's not a "ground meat" category. When the meat is raw, grinding it won't change the proportion of fat by weight, but when you cook ground meat the fat escapes much more easily than it would if you cooked the whole cut(s) from which the meat was originally ground.

Here's some further reading from Texas A&amp;M about ground beef labeling, for those who are interested.