I read through it and read through the FAQ for adoption: https://mariadb.com/bsl-faq-adopting/
The question I have, is they say:
"On the Change Date, or the fourth anniversary of the first publicly available distribution of the code under the BSL, whichever comes first, the code automatically becomes available under the Change License."
Later on however in the FAQ they write,
"Q: Will the Change Date remain constant?
A: The answer depends on the company providing the BSL software. At MariaDB, the answer is no. Each new major version of the software will have its own Change Date."
and
"Q: What is considered a major version for there to be a new BSL and new Change Date?
A: The answer depends on the company providing the BSL software. At MariaDB, it would be a version that does not only fix bugs but adds features."
It is unclear to me, given those later Q and As, if the first line I quoted is saying 4 years from the release of each version of the code, or the first public release of any of the code.
What is the correct way to interpret this?
I will likely consult a Lawyer as well if I do go to use this but I figured some people here may already be knowledgeable.
In theory 4 (or whatever) years later some version will become licensed under Open Source license but by that time it will be well past EOL ridden with bugs and security holes and unsafe to use.
Of course (in theory) you could take on maintaining such version yourself in practice it does not make any practical sense