Cabbage – volume to weight conversion

Rinsing the sauerkraut absolutely does work - we do it all the time, both with store-bought and homemade sauerkraut. Every batch of sauerkraut is different, so rinsing & tasting is the only way to ensure that your dishes turn out appropriately salted. Yes, some of the salt has entered the cabbage itself, but most of it will be in the brine/on the surface.

If rinsing in a colander isn't enough (and if you used twice the recommended amount of salt it's likely not to be), then you can drain the liquid as best you can, then add clean water to cover, and let it soak. Rinse and repeat until the salt level tastes more acceptable.

Adding more cabbage and letting it ferment some more is also an option, although the twice-fermented parts can end up rather mushy.

Per NC State's Extension's article on pickles and sauerkraut (some emphasis added):

Pickles or sauerkraut mold during fermentation.

Answer:

Unsafe—microorganisms are growing improperly.

Possible reasons

• Fermentation temperature was above 75°F.
• Too much salt was used, not allowing adequate lactic acid production.
• The cloth on top of the kraut was not kept clean during fermentation (may need to be replaced after skimming).

Per Penn State Extension's Saurkraut Guide (emphasis added):

Do not taste it if you see mold on the surface, feel a slimy texture, or smell a bad odor.

Their PDF on Saurkraut says:

To avoid surface mold growth, keep the cabbage submerged at all times by covering it with a plate just small enough to ft inside the fermentation container or with two or three clean quart jars filled with water. An acceptable alternative is to fill a large, sealed, food-grade plastic bag containing 4½ tablespoons of salt and 3 quarts of water.

Again, no indication of acceptable types of mold.

I cannot endorse the existing answers which indicate that mold is an acceptable part of the saurkraut making process, unless credible science based evidence is presented, from reputable sources such as University Extension Centers or, better yet, peer reviewed journal sources.