Does DAML have its own interoperability layer or is Canton DAML’s interoperability layer?

Ed: Split out from DAML support for Azure, Vuejs, Graphql, QLDB & Canton

I’d say the answer is “yes” to both parts of your question. The Canton protocol is DAML’s interoperability layer. The Canton committers and mediators can run on different Blockchains / DLTs to provide consensus and data exchange for a DAML Ledger. The Participant Node is able to connect to many such DAML Ledgers and transact across them thus providing true interoperability.