Hm, wasn't one of the conditions to use BSL (the name of the license) that one of the "Change licenses" must be GPL?
I remember distinctly because while I liked BSL, I never understood why I couldn't use AGPL as fallback (which would be much better suited to my use case).
EDIT: It seems I was wrong:
> To specify as the Change License the GPL Version 2.0 or any later version, or a license that is compatible with GPL Version 2.0 or a later version, where “compatible” means that software provided under the Change License can be included in a program with software provided under GPL Version 2.0 or a later version. Licensor may specify additional Change Licenses without limitation.
I remember distinctly because while I liked BSL, I never understood why I couldn't use AGPL as fallback (which would be much better suited to my use case).
EDIT: It seems I was wrong:
> To specify as the Change License the GPL Version 2.0 or any later version, or a license that is compatible with GPL Version 2.0 or a later version, where “compatible” means that software provided under the Change License can be included in a program with software provided under GPL Version 2.0 or a later version. Licensor may specify additional Change Licenses without limitation.
https://mariadb.com/bsl11/
So Apache is OK, because such software can be incorporated into GPL app. AGPL is not, because it places additional restrictions.