I believe that the Bitcoin Foundation's argument is that in California BTC doesn't meet the definition of a currency.
That's irrelevant as it never went to court therefore it's not case law like the Texas ruling is.
I've read various portions of California law and they are very explicit. They uniformly define "money" as something authorized by the U.S. or foreign governments. The laws distinguish between "money" and "monetary value", and in many cases the two are treated differently. Granted, these definitions apply only to the specific context (in this case, California financial regulations).
From the California Financial Code
2000. This division shall be known and may be cited as the Money Transmission Act.
...
2003. For purposes of this division, the following definitions shall apply:
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(m) "Monetary value" means a medium of exchange, whether or not redeemable in money.
(n) "Money" means a medium of exchange that is authorized or adopted by the United States or a foreign government. The term includes a monetary unit of account established by an intergovernmental organization or by agreement between two or more governments.