The Business Source License is not an open source license.
Sources:
> https://spdx.org/licenses/BUSL-1.1.html
"The Business Source License (this document, or the “License”) is not an Open Source license. However, the Licensed Work will eventually be made available under an Open Source License, as stated in this License."
The code eventually becomes open source after certain criteria are met. No one in this thread claimed that BSL-licensed code is immediately open source.
Features start in the most expensive tier, then tricke down and end up in OSS.
(and note that cost-effectiveness != cost -- they're correlated, but not the same)
For instance, not all companies are happy with third parties that have access to their data, either directly or indirectly.