[wellylug] Writing commercial apps which connect to GPL software.

[Peter Harrison]

On Sat, 29 Mar 2003 22:22, Nigel Walters wrote:

> Now often his clients have MS Office without MS Access. Instead of
> advising them to upgrade and buy Access he would like to be able to
> write his application in Visual Basic and use an ODBC link to MySQL (or
> another GPL'ed database)
>
>
> Reading of the MySql licence page would seem to imply that he would run
> into difficulties doing this !!??
> (http://www.mysql.com/products/licensing.html).

This is an interesting problem. The problem is in the interpretation of 
'linking'. Basically the GPL says that any application which links to GPL 
code must be released as GPL. Therefore if you do not comply with the GPL you 
must obtain a license to the required code under commercial terms. Generally 
'linking' refers to the build process of a binary, and the GPL covers both 
static (including code directly in the binary) and dynamic (linking again 
compiled libraries) code.

However, MySQL AB appears to extend this definition to include linking to the 
application at runtime - ie via TCP/IP. The implication here seems to be that 
only GPL client applications may connect to GPL server applications.

Clearly it is not the intent of the GPL that it will only let other GPL 
software communicate with it. For example, if sendmail were GPL would it mean 
that only GPL client applications could send mail through them? Other 
questions could relate to cut and paste - if you could 'link' a GPL 
application to another in any way it would force the other application to be 
GPL. Clearly such an interpretation is far too wide to be enforceable. 

There is a secondary argument relating to MySQL - and that is that bundling 
MySQL with your application could be considered infringing apon the GPL. 
However, this argument is rather poor as well, since this would mean that 
storing GPL software on the same CD as non-GPL software would mean the 
non-GPL would need to be licensed under GPL. Clearly this is also far too 
wide.

The intent of the GPL is to enforce the right of the user to use, modify and 
distribute the software in question. As long as bundling your application 
does not prevent users from exercising these rights - ie you should provide 
MySQL source on the same CD - you should have no problem distributing it 
legally.

However, this is *not* the interpretation of MySQL AB, and I personally 
wouldn't want to be the one going through a legal battle to find out which 
definition holds up legally.

> I initially assured him that as he is not linking his code directly to
> MySQL only indirectly and he is not changing MySQL itself he is
> OK...however that is NOT what the mysql licensing
> page says.

See above - MySQL AB's definition of linking is too wide.  I would suggest 
using PostgreSQL if you want a database that is sure to avoid this kind of 
politics.



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