However, MongoDB selected a free and open source license. This was always in the cards. They went with AGPL to keep the source maximally open for end users, but that never protected their revenue stream. (Some JS SDK companies used it for that purpose, where it makes some sene, but a DB is very different.)

But if they had started with something proprietary uptake would have been very likely much less. And people would have continued to use mysql or Cassandra if they really needed something "webscale".