I don't think he's saying that eloqdata itself contains AGPL code from Mongo. Rather, their other project, eloqdoc, contains AGPL code from Mongo, and a user might want to integrate the two, so for simplicity eloqdata is offered under both licenses.

In that case, a user wanting to distribute eloqdata and eloqdoc together need only adhere to the AGPL, not both licenses.