SQL is an ANSI and ISO norm but maybe IBM kept the trademark ...
I Know PostgreSQL extend language with their own command. I don't think it's a problem so if you want to create a awesome database, let's go :)
Do I have to buy/take license/permission for have SQL (as in PostegreSQL) at the end of my software's name?
No, but if you're not at least making an effort to conform to the standard, or designing your system around different concepts entirely, you're going to confuse a lot of people by calling it somethingSQL.
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