I'm not exactly certain how bukkake or gokkun started (MilkyCat seems to have played a part in the 1990s), but facials have been popular in porn for a long time; long before the Japanese started doing bukkake videos. US porn has always put a focus onto the "money shot." The makings for bukkake were always there. Perhaps the censorship was part of the impetus to form a new genre based entirely on cumshots, but it surely has role or purpose any more.
So yes, there would be bukkake and gokkun without censorship. Urabukkake proves this, and the US industry has many of their own lines of bukkake and gokkun porn that are completely uncensored, as does Germany, France, & Spain. The question of whether censorship was an impetus for the genre isn't exactly a closed case. Anyway, censorship was never a requirement for making cumshot-focused porn anyway. Censorship has and always will be a blight on the porn industry of Japan. It's one of their biggest blunders, not only because it is illogical and annoying. It's hurting their profit margins as well due to decreased lack of sales. There are thousands of people that would undoubtedly care about Japanese porn (I've personally talked with hundreds) if it were not for the pixellated pussies and dicks. There's a global economy, and the Japanese, through their censorship, are basically rendering their own porn inferior and reducing their international sales. Japanese will undoubtedly be the biggest purchasing demographic of Japanese porn, but Americans and Europeans outnumber the Japanese and are the biggest porn consumers on the planet, so the negative monetary effect on the Japanese porn industry is still worth considering.
I mainly dislike censorhip in bukkake/gokkun because you can never see the girl's lips wrap around a dick, which is one of the hottest sights in this world. Thankfully they're not so illogical as to consider human gametes worth censoring also. That would mean the sperm itself would need to be censored.
Girl covered in sperm drinking a pint glass full of human semen? Allowed
Showing a natural human penis (an anatomical feature that has kept the human species alive, which every male legislator possesses.) Forbidden.
Just wanted to add that Milky Cat wasn't the first to really start the bukkake "craze". The first to really focus on huge numbers of shots only and, for what I can tell, more-or-less popularized the term "bukkake", was Shuttle Japan. Earlier than that was the Jesus Kuritorisu*Superstar series which was a more mainstream version of Shuttle Japan's bukkake focused videos, but generally did not have the same quantity of shots. Mainstream sperm focused vids might have 10-20 shots at most whereas Shuttle would have 40 or more. I'm not sure why Shuttle fell off the map, though I reckon a google search would pull up their history. MVG or M's Video Group was another Shuttle Japan like company that would have huge bukkake and gokkun sessions. Unlike Shuttle they are still around and still do sperm themed videos as any fan knows.
There are other players in the early history of bukkake, but I can't think of anything that isn't well known by most fans.
*Kuri means nut
, to means and, and risu means squirrel. Nuts in the mouth of the squirrel looks like someone with a certain body part in their mouth when performing fellatio. Kuritorisu means clitoris. Jesus Kuritorisu Superstar is a play on words of Jesus Christ {kiristo} Superstar, the movie and play... So, yeah, who says Japanese aren't creative?!