I have
bulldog database in progress
Wow.... this is amazing. Does anyone know of a site that can make databases and also has interactive variant boards? If so, this would be awesome to play through. Love it!

Question:
On avarage, how many good book moves are there from a given, frequently occurring opening position?

Question:
On avarage, how many good book moves are there from a given, frequently occurring opening position?
Depends how you define a "good book move" and what your bar is for a position to be "frequently occurring".
My answer would be 0, since I think of book moves as established theory, which there is none. Just because a move has been played a lot does not make it theory to me. Even if someone would try to come up with theory I wouldn't trust it if it didn't come from a player that I recognize as stronger than myself.
But that is just me though, I know several members have had some fun naming openings in this group.
As an example, I think 1.e4 e5 is a dubious opening for black, but it is hard to call e5 a bad move. However, who knows maybe sometime a player manages to play that opening really well and prove me wrong and I change my mind. Then it could suddenly become a good opening.

I suspect 1. e4 e5 is "sharp" rather than "dubious". Black needs to be accurate to avoid giving too much to white, but if black is accurate, I'd be surprised if white can force an advantage. The problem is that very few people here are accurate in the opening. I'm certainly not. I'd say the only two people who are accurate in the opening are Martin and landontu.
As for "established theory", it classic chess that term is used for openings that are older than USA in many cases. We're not going to see any of our openings become "established theory", not unless we see a stockfish-level engine taking a look.

I guess the term "established theory" is not really that important. The important part is whether it is good enough for opening preparation, which differs for different playing strength.
A database really helps opening preparation a lot, it's just that "book move" is a term I prefer to stay away from. If you look through a game and look for mistakes, then "book moves" is not moves you should be looking at, but rather when you are out of book.

The term "book move" literally comes from the fact that throughout the history of chess, opening books have been the go-to resource for those seeking to strengthen their opening knowledge. Even today books are still important, I have a box full of opening books. So I would use that term to refer to opening moves that have been well studied, but then the term "well studied" is also subjective. Certainly, nothing we've played is "well studied" though.

I played 1...g6 first though:
https://www.chess.com/forum/view/chess-variants/big-dog-2-game-jamesagadir-vs-martin0
I even used it against @captaintugwash
https://www.chess.com/forum/view/chess-variants/mega-dog-winners-semi-final-captaintugwash-martin0

I played 1...g6 first though:
https://www.chess.com/forum/view/chess-variants/big-dog-2-game-jamesagadir-vs-martin0
I even used it against @captaintugwash
https://www.chess.com/forum/view/chess-variants/mega-dog-winners-semi-final-captaintugwash-martin0
Your second move both games was f5. I typically go Wg7.
1. e4, g6- Swedish Defense
2. ?, f5- Swedish Defense
2. ?, Wg7- Swedish-Mark Defense

Feel free to continue, but here's a bit of a warning.
There is a limit to how much content can fit into a post. If I try to post a list of all completed games, then I get the response "Post is too long".

But it is SO SO much better and easier to play compared to black in bulldog chess. In normal chess, the difference isn't as notable in my opinion
1. e4: 36
1... g5: 7
2. d4: 5
2... c6: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-group-4-game-kingsindianattack7-vs-rychessmaster1
2... f6: 2.
3. Nd3: 2 https://www.chess.com/clubs/forum/view/worldcup-game-bad-dobby-fischer-evert823, https://www.chess.com/clubs/forum/view/gigadog-tournament-game-captaintugwash-evert823
2... Ng6: 2.
3. Nd3: 2
3.... f6: 2.
4. Bg4: 1. https://www.chess.com/clubs/forum/view/megadog-tournament-chess-condor-thegreatauk
4. Wd2: 1 https://www.chess.com/clubs/forum/view/giga-dog-tournament-game-thegreatauk-bad-dobby-fischer
2. Wd3: 2
2... Wg7: 1 https://www.chess.com/clubs/forum/view/bulldog-chess-rychessmaster1-evert823-computer-with-witch-and-guard
2... c6: 1
3. Ng3: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-group-4-game-landontu-vs-rychessmaster1
1... e5: 6
2. d4: 3
2... exd4: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-coogleschess-haoming09-with-witch-and-guard
2.. f6: 2.
3. Nd3: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-coogleschess-haoming09-with-witch-and-guard
3. h3: 1. https://www.chess.com/clubs/forum/view/a-micro-dog-2-game-2-aronian22-haoming09
2. Wd3: 1
2... d6: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-game-deeper-thinking-v-s-kingsindianattack7
2. Nd3: 1. https://www.chess.com/clubs/forum/view/bulldog-w-witch-yujieli-vs-johnhs
2. Ng3: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-aronian22-ethantan
1... Wg6: 7
2. d4: 3
2...Bi6. https://www.chess.com/clubs/forum/view/worldcup-game-evert823-mathsmaths0
2... f5: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-worldcup-game-kingsindianattack7-landontu
2... c6: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-group-1-game-aronian22-vs-pandasawesome
2. Ng3: 1. https://www.chess.com/clubs/forum/view/micro-dog-7-game-2-perpetuallypinned-pandasawesome
2. Bg4: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-deeper-thinking-v-s-landontu
2. Wd3: 2.
2.... Bi6: 2.
3. Ng3: 1. https://www.chess.com/clubs/forum/view/micro-dog-1-final-pandasawesome-mathsmaths0
3. Bxi6: 1. https://www.chess.com/clubs/forum/view/a-micro-dog-1-game-1-landontu-pandasawesome
1... g6: 4
2. Ng3: 2
2..f5 3. exf5 gxf5: 2.
4. f4: 1 https://www.chess.com/clubs/forum/view/giga-dog-winners-quarter-final-haoming09-chess-condor
4. Nd3: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-group-3-game-justarandompatzer-vs-marks1420
2. f4: 1. https://www.chess.com/clubs/forum/view/micro-dog-2-championship-aronian22-v-marks1420
2. d4: 1. https://www.chess.com/clubs/forum/view/giga-dog-tournament-game-bad-dobby-fischer-marks1420
2. c4: 1
2... f5: 1. https://www.chess.com/clubs/forum/view/giga-dog-tournament-game-round-2-winners-pandasawesome-vs-marks1420
1... e6: 3
2. d4: 1. https://www.chess.com/clubs/forum/view/worldcup-game-evert823-supersam1
2. Nd3: 1. https://www.chess.com/clubs/forum/view/giga-dog-winners-quarter-final-martin0-johnhs
2. Ng3: 1.
2... Bg5: 1. https://www.chess.com/clubs/forum/view/micro-dog-4-final-sollieman83-amusingmouse
1... Ng6: 4
2. Wd3: 1.
2... e5: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-group-3-game-marks1420-vs-sollieman83
2. d4: 3
2... h6: 1. https://www.chess.com/clubs/forum/view/micro-dog-6-game-1-perpetuallypinned-joeydeng
2... f5: 1.https://www.chess.com/clubs/forum/view/mega-dog-losers-final-thegreatauk-justarandompatzer
2... Wh6: 1. https://www.chess.com/clubs/forum/view/giga-dog-tournament-game-mathsmaths0-justarandompatzer
1... c6: 1
2. d4: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-mathsmaths0-vs-supersam1
1.. Nd6: 2. https://www.chess.com/clubs/forum/view/micro-dog-6-game-2-awesomeben-bigbigbig360 1-0
2. h3: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-deeper-thinking-rychessmaster1
1...f5: 1
2. exf5: 1
2... Qxf5: 1
3. Ng3: 1
3.... Qf8: 1. https://www.chess.com/clubs/forum/view/micro-dog-2-game-1-aronian22-thegreatattorney
1. f4: 4
1... g5: 2
2. fxg5: 1
2... Wg6+: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-cooglechess-evert823-with-witch-and-guard
2. Nd3: 1.
2... Wg6: 1. 0-1 https://www.chess.com/clubs/forum/view/bulldog-chess-6-final-perpetualpinned-vs-bigbigbig360
1... Wg6: 1.
2. Nd3: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-world-cup-ethantan2509-pandasawesome
1... f5: 1
2. Wd3: 1
2... Wg6: 1
3. Ng3: 1. https://www.chess.com/clubs/forum/view/micro-dog-5-game-1-nikic007-queenpawnendgame
1. d4: 1
1... f5: 1
2. Nd3: 1. https://www.chess.com/clubs/forum/view/giga-dog-tournament-game-horribletomato-kingsindianattack
1. Wd3: 2
1... f5: 2
2. d4: 1. https://www.chess.com/clubs/forum/view/a-micro-dog-bronze-match-pandasawesome-rychessmaster1
2. e4: 1. https://www.chess.com/clubs/forum/view/giga-dog-tournament-game-musketeerchess2017-jamesagadir
1. Bb3: 1
1... f5: 1
2. d4: 1
2... Nd6: 1
3. Wd2: 1. https://www.chess.com/clubs/forum/view/giga-dog-game-28-rychessmaster1-vs-horribletomato
1. Wc3: 1
1... f5: 1
2. Ng3: 1. https://www.chess.com/clubs/forum/view/micro-dog-5-final-queenpawnendgame-deeper-thinking
1. i4: 1
1... g5: 1
2. e3: 1. https://www.chess.com/clubs/forum/view/old-dog-tournament-final-supersam1-thegreatauk?page=1&newCommentCount=1#last_comment
1. Ng3: 2
1... f5: 1.https://www.chess.com/clubs/forum/view/bulldog-chess-johnhs-evert823-theweirdengine-with-witch-and-guard
1... e5: 1
2. h3: 1. https://www.chess.com/clubs/forum/view/bulldog-chess-with-witch-icositetrachoron-awesomeben