Free *LIBRE* includes right to make changes & pass them on

If someone controls who makes changes to the code, it's not free (libre). I could, theoretically, take MariaDB and fork my own version. I could even do that with Linux (note: in neither case would I recommend ANYONE use my fork - but I could). With BUSL, only the original vendor can do patches. I can't even use the code in production without a license.

IFF patches to the older versions fall under the OLD (GPL at a set date license) does the software become LIBRE. The vendor is free to continue patching, but only if they keep the license GPL does it remain LIBRE. That's the issue here - when exactly does that transformation from BUSL to GPL occur? If the vendor puts in one patch into the old code, does that reset the clock? Or are those patches GPL? And who decides / how is the decision made? From a legal/liability standpoint, it matters.

Note that, for any patches not from the vendor to the GPL version, those patches CANNOT legally be pulled into the latest BUSL version of the code - BUSL does NOT grant the same rights as GPL, and is thus incompatible with it.

The answer to support for FOSS for companies willing to pay is for them to pay for developers of the open source software. There may be foundations (such as The Document Foundation and the Linux Foundation), companies (Canonical, Red Hat, Collabra among others), or pay to individuals. Budget 1/2 what licensing of the proprietary software would cost (heck, even 100%). You get your needs prioritized, you get the software fixes, and you always retain the option to change support vendors.