Communication over a specific, not documented protocol, that only works with one product, will from a GPL point of view be seen as a combined works and then the licenses must be compatible.
You can use non GPL connectors with MySQL as MySQL's protocol is well documented and MySQL has always encouraged others to implement connectors for MySQL. This is why InfiniDB could leverage connections to MySQL.
It is still not 'completely safe' to assume that one can add a closed source storage engine to MySQL or MariaDB by claiming that the storage engine interface code is GPL. If the storage engine node code only works with MySQL, the GPL will still apply to it.
What is the license of the FoundationDB connector/API implementation code?
If that has the Apache license, then it cannot be used with ColumnStore.
Communication over a specific, not documented protocol, that only works with one product, will from a GPL point of view be seen as a combined works and then the licenses must be compatible.
You can use non GPL connectors with MySQL as MySQL's protocol is well documented and MySQL has always encouraged others to implement connectors for MySQL. This is why InfiniDB could leverage connections to MySQL.
It is still not 'completely safe' to assume that one can add a closed source storage engine to MySQL or MariaDB by claiming that the storage engine interface code is GPL. If the storage engine node code only works with MySQL, the GPL will still apply to it.
What is the license of the FoundationDB connector/API implementation code?
If that has the Apache license, then it cannot be used with ColumnStore.