1) the sever architecture(s) are different (information_schema. system variables, implementation of SP)'s triggers, dta type differences etc.)
2) the SQL 'dialects' are different. Most important MySQL SHOW statement is not supported by MS SQL.
3) the is no parallel to the MySQL C-API
so every byte of code related to how to communicate with the server would have to be rewritten.
However what code there is defining the GUI would still mostly be usable.
So .. lets's say that 33% – 50% of the current code would go into a version for any other database server.
We have no such plans!