GPLv2 was written in 1991. GPLv3 changes the wording in Section 3(a) to "durable physical medium", but at the same time it gives other possibility including "C

GPLv2 was written in 1991. GPLv3 changes the wording in Section 3(a) to "durable physical medium", but at the same time it gives other possibility including "Convey the object code by offering access from a designated place (gratis or for a charge), and offer equivalent access to the Corresponding Source in the same way through the same place at no further charge". Everyone was doing network distribution of GPL software long before GPLv3 came out, effectively treating a download as a medium customarily used for software interchange. Not a physical one, but GPLv2 does not say anything about that.