Dog Peeing all over the house

Two things.
1) Training him to go on the porch means that he may be confused and think that the rest of the house is fair game. He may be having trouble distinguishing the two -- the porch, for him, just appears to be an extension of the house.
2) Territoriality. As in, here are some other dogs, but this is my house, dammit! So I'm gonna mark it. Everywhere.

And, actually, a third thing.
3) At nine months, he's essentially a teenaged dog. They can be problematic from something like eight to fifteen, sixteen months or so. As in, bored chewing problems and other kinds of acting up, including all sorts of training issues.

Is the peeing a steady stream, as in, he's relieving himself, or is it little squirts everywhere? Little squirts are a sign that it's territoriality. If it's a steady stream then it's toiletting. For how much time do you leave him during a typical day (if at all)? How often between walks? A normal dog of that age needs at least two good walks a day. This is not only to get him to do his business but also to tucker him out and give him some intellectual (yes, I said that) and emotional stimulus.

One thing you can do is train him to go on walks with a command. As in, take him to wherever is appropriate and tell him to "do your business". Then lavish praise if he gets it right. Another idea is canine activities. The more socializing, the better. If he's having issues with his doggie roommates then more socializing can help with that.