The "official" free-software and open-source definitions are slightly different, with the නිදහස්-මෘදුකාංග definition generally considered to be more strict, but the විවෘත මූලාශ්‍ර licenses which are not considered to be free software licenses are generally obscure, so in practice virtually all open source software may also be considered free software (a notable exception being the Netscape Public License used by Netscape Navigator and Mozilla).