There is currently no readily available evidence that George Soros has funded snopes.com, nor are the financial record for snopes, Soros, or financial entities they control open to inspection (what would be necessary to falsify the claim). The claim is analogous to Russell's Teapot.
Here is an independent opinion from TruthOrFiction.com, a similar themed site:
Snopes.com is an excellent site that has become an authoritative source for information about urban legends and forwarded emails. We regard David and Barbara Mikkelson, the founders and operators of Snopes.com, as colleagues and professional researchers who have earned a good reputation for what they do.
We can give a unique perspective on this story because we do the same kind of work as Snopes.com and have sometimes been the target of similar criticism.
We’ve got a collection of emails that have come to TruthOrFiction.com accusing us of being “right wing whackos” as well as “liberals” and “communists.” We’ve been suspected of being owned and operated by both Republicans and Democrats. We’ve been called “Christian propagandists” as well as “atheists pretending to be neutral.” We occasionally receive emails that have elaborate theories about who “really” owns us and what our “real” motives are.
The bottom line is that if you try to report the truth, there will be those who don’t like the truth you’ve reported and who will develop suspicions about why you did.
That, in our view, is what is happening with Snopes.