What I dislike about BSL and related is that on the Change date the software typically reverts to GPL, which prohibits others from creating their own BSL competitor to MariaDB.
What I would like is to take the MariaDB 4 year old source and release my own database with better features, then compete in the market place with MariaDB, and have my own commercial exclusivity period, as I have explained elsewhere in the thread:
https://news.ycombinator.com/item?id=32339945
To use the BSL in the sense I am referring here, the Change license must be BSL itself, with flexibility to allow a new change date, at the new developer's discretion, no longer than a set limit (4 years for BSL). If want to make the code free-beer, I set the change date to be the same as the release date, but the next day every other developer has the option to fork my BSL code and release their own BSL time-bombed version for up to 4 years and make money of it. Users who don't want that can take my code and enjoy all the freedoms that GPL would grant. [1]
Otherwise, if my only option on the Change date is GPL, which is very restrictive to me as a developer, I have zero incentive to work on certain types of free software that can't make money off support.
In a sense, a recursive BSL is freer than GPL, because I grant my users all the freedoms of GPL but additionally the freedom to create their own timed-bombed commercial release, i.e., to restrict the freedom of others with their own releases. The end users then have to option to use my original free-beer version, or pay for a better feature set, which itself is guaranteed to become free beer in a number of years. This incentive structure ensures a steady revenue stream for the developers as long as they create new features which are desired, but the revenue stops if they try to rely on vendor lock-in.
[1] (of course to do this recursive-style licensing one would need to modify BSL to grant the actual freedoms to run the code, distribute etc., the current text lacks this and relies on an external open source change license after the Change date).