Whether FOSS implies open membership is a matter of semantics. FOSS can refer to the development model (bazaar vs cathedral), the community, attitudes ("patches

Whether FOSS implies open membership is a matter of semantics. FOSS can refer to the development model (bazaar vs cathedral), the community, attitudes ("patches welcome" as a way of saying "well do it yourself then", meant sarcastically as "patches welcome" is repeating the implicit), or ideological stance (blah blah freedom). So I don't think "does FOSS imply open membership" even has an answer.