MySQL is distributed under the GPL and there are trademark and other legal requirements -- check here for details.  We are certainly aware of the recent acquisition of MySQL by Sun Microsystems, but we are committed to staying with the GPL constraints and don't anticipate any legal issues to arise.

• How is this licensed?  We are using the GPL version of the product as distributed from the primary MySQL web site.   You can see the GPL terms here distributed in a MySQL distribution from MySQL AB.
   
• How can you sell this?  That is not prohibited by GNU licensing. 
  
  The excerpt below comes from the GNU web site licensing FAQ.

If I use a piece of software that has been obtained under the GNU GPL, am I allowed to modify the original code into a new program, then distribute and sell that new program commercially?

You are allowed to sell copies of the modified program commercially, but only under the terms of the GNU GPL. Thus, for instance, you must make the source code available to the users of the program as described in the GPL, and they must be allowed to redistribute and modify it as described in the GPL.

Similar information is presented for licensing at the MySQL AB site.
 
We are not even selling a new commercial product,  but only charging for the service of having us prepare, test, store and deliver a precompiled component to you for current and older MySQL versions.
 
• What about your relationship with MySQL AB/Sun Microsystems?  At present there is no formal relationship between our companies.
 

• Who are you?
  
  The Software Workshop in a privately held company incorporated in the state of New York in 1995. Check here for more information on our unique makeup.
   
• Why wasn't this done within the primary MySQL & PostgreSQL distributions?  
  
  We thought we had a great idea for an extension to the MySQL server to help DBAs.  We felt it would not only be a good change for SQL but also other DB servers from Oracle, IBM, and Microsoft, and should become a SQL standard extension.   We also felt we could make some money by supporting back-ported versions of the extension to earlier SQL versions.  Time was critical and we felt faster progress toward these goals could be made by one company being lead in this area during initial development and release.
   
• Are you trying to 'branch' MySQL or PostgreSQL?
  
  No.  We fully expect members of the MySQL & PostgreSQL communities to review our server changes and that modifications will happen as code is reviewed by developers and most importantly, as DBAs give their feedback about what they want to see in SQL Extended Statistics.
  
  We would continue to perform new development and offer the service of precompiled binaries for earlier versions of MySQL of PostgreSQL.