There have been many questions as to the viability of MySQL's
assertion that it can dictate what constitutes a derived work in order
to use the GPL against developers who don't wish their software GPL'd
and force them to pay for a commercial license.
According to the lawyers I've consulted, based on the letter of the
GPL, here is the conclusion:
Commercial users of MySQL opting for the GPL'd version are not
compelled to release their applications under GPL and may use it
freely with their applications provided they do not incorporate any of
the interface code provided by MySQL. In other words, if you use the
ODBC interface, you are not GPLing your software by association. If
you use the MySQL C-library interface, compiled into your application,
then it's GPL'd.
The simple act of connecting to a database by TCP/IP is does not
constitute a derived work of the GPL'd server. Building your own
C-library interface based on the protocol information you can
extrapolate from their C-library source does not constitute a derived
work. Distributing a GPL'd application and source on the same CD as
your proprietary application, as per the conditions detailed in the
GPL, does not constitute a derived work.
Basically, there is no reason why a commercial user cannot use the
GPL'd version of MySQL freely and without worry.
A developer cannot impose its own restrictions over the GPL unless
they release their own license. MySQL AB states, on their website,
that the GPL released version is 100% GPL, meaning that the terms and
conditions of the GPL apply. If they choose to release it under a
modified version of the GPL, then it is not 100% GPL and they need to
provide this license clearly on their website. It would essentially
become a MySQL AB Public License (not GPL) with conditions that
restrict users as they please.
In other words, you cannot say, "this software is a 100% GPL release
but if you're a commercial user then you can't use it under GPL with a
proprietary application", simply because the GPL makes no such
restriction. This claim is no different than saying, "If you connect
to Linux over the network with Windows, then Windows must be GPL'd." -
a bullshit assertion. This kind of restriction would require MySQL AB
create their own free-use license with such a specific condition.
Conclusion: Yes, Virginia, you can use the GPL'd version of MySQL with
your proprietary software.
