SNS-1 ledger transaction history?
To query the ledger transactions, you could for example use this tool.
There is an SNS1 proposal out that proposes to upgrade the SNS1 DAO to a new version. If this proposal is approved, the ledger will be upgraded to a WASM that exposes the candid and as an effect you can see the ledger API more easily on the dashboard.
Moreover, we are planning on adding a better dashboard for the SNS.
SNS-1 dapp source code?
The dapp is the standard asset canister. I am pulling in people that worked on the details here and we are looking into how we can best publish this.