Yes, I researched this, and my wife is also an experienced lawyer and works in the judiciary system, prior her current job at family tribunal, she worked in commercial sections.
There are many laws here that forbids using any currency that's not the national one, from consumer's laws to financial laws.
1) By your interpretation, there's a law in Brazil that prohibits the use of any currency that is not Brazil's national currency.
2) Because Bitcoin is not Brazil's national currency, you are now worried because NameCheap is now using Bitcoin, and will drop your company accounts with them.
So my main question is: why weren't you worried when Namecheap started accepted US Dollars (i.e., since their founding)? After all USD are not Brazil's national currency. Does this law distinguish between USD and other currencies? This is not the case according to the case you cited.
Most importantly, the law you refer to above, and the case you cited, all seem to involve government payments. And you've cited no other specific laws, other than this one (LEI Nº 4.595, DE 31 DE DEZEMBRO DE 1964), which is basically the law governing the establishment of a national currency. So according to this law, you have to pay the Government of Brazil in Brazilian currency (reales) for taxes, government contracts, etc. This is entirely reasonable; the US Government has a similar law. In the US, at least, this law does not outlaw the use of other currencies. And since multinational corporations do business in USD in Brazil every day of the week, it seems to me extremely unlikely that this outlaws the use of foreign currencies in Brazil. You just can't pay Brazilian government taxes or for other government services in other currencies.
Even though I do have credentials to keep this discussion going forever, I'll refrain from further comments on this thread. You are not willing to understand what I'm saying so my comments are pointless.
As far as I can tell, you have yet to explain how what Namecheap does with other people could effect you, if you simply choose to not use bitcoin to pay them. You haven't given us anything to fail to understand...
There are many laws here that forbids using any currency that's not the national one, from consumer's laws to financial laws.