I do live in SF, and this is an interesting turn of events, because SF is a case of a city that does not have a homebrew club and yet has many homebrewers. (There was a club, once upon a time, but it seems to have disappeared.) This CSA feels like an interesting way to meet other brewers; it feels, in fact, like a homebrew club in many ways, except less emphasis on the meeting and more on the sharing. I really liked the homebrew club I briefly belonged to in Florida before we suddenly moved back to CA, and I miss the camaraderie, advice, beer-tasting, etc. The Bay Area has some very good homebrew clubs, but SF proper doesn't, and if you live in the area you know that traffic and bridges make a seemingly short distance pretty challenging to get to.
I won't comment on the legality (I even have an IANAL button somewhere), except to note that the first homebrew I ever had was shared with me on the dunes of SF's Ocean Beach several years before homebrewing became legal... I didn't know at the time that it was illegal, but I do have to note that it was hardly the only illegal activity known to happen in SF at the time; if anything, in those days beer was considered kind of "square."