In France the notion of "charity" is tied to a restrictive list of associations so recognized by the state; a donation is tax-deductible only if to one of these organizations. I've donated e.g. to Unicef on a tax-deductible basis.

That will not apply to my donations to SIAI. (On the other hand, I can't (yet) bring myself to think of SIAI as a charity. I donate mainly to encourage the continued existence of LessWrong.com - if the promotion of rationality is "spun off" to a daughter organization as the SIAI strategic plan suggests that's what I will continue donating to in the short term.)