You absolutely cannot use the BSL code in production without a commercial license. That's literally the first thing it says:

> The Licensor hereby grants you the right to copy, modify, create derivative works, redistribute, and make non-production use of the Licensed Work. The Licensor may make an Additional Use Grant, above, permitting limited production use.

Maybe specific software modifies that as you say, but the base BSL doesn't. I agree it's super vaguely worded ("production" isn't defined at all). Also it turns out MariaDB itself isn't BSL licensed - it's GPL, just some extra projects around it.