I read Steven’s article on dual licensing with mixed feelings: I think there’s a nuance missing. First of all, dual licensing is not about retracting a more appealing offer. It’s about two concurrent offerings for the same or a different product.

Whether the offering is for the same product or for a different product is what matters.

Open Source should be about what it says: have the source openly available. As the copyright owner of a product, one can offer a separate license to paying customers, as I think e.g. Qt does. Get a “viral GPL” license for free as in beer or pay for a “closing source appealing license”. (I don’t know of any examples of dual licensing based on BSD style license, I guess those would be pretty useless commercially.)

So the difference that matters in pure dual licensing (for the same product that is), from a Free Software / Open Source point of view, is basically the difference between the two big churches, Gnu and BSD. (Within Gnu, some even argue KDE is more Free as in Speech with Qt’s dual licensing than Gnome/GTK with LGPL.)

I’m not sure wich model Steven prefers, but maybe a BSD-style license for his MySQL example so one does not have to buy a closing source license. (A Closing Source License is a license where you buy (pieces of) source code that are closed source and must remain closed source.) I might misunderstand him of course but I won’t go into that religious war now. The thing is this case is not that bad as the same source remains available for paying as wel as non paying customers. (Well, not for the customer of the paying customer, but more of that later.)

The important thing so far is that all the same source is openly available to the vendor’s customers and users.

It’s al whole different matter when dual licensing comes with different products. You get one edition in open source, and need to buy a closing source license for another edition with more goodies. In this case you really have pieces of code that mandatorily remain closed source. That is not a good thing.

Note that the difference can be subtle. Here the example was about the vendor doing closed source stuff, which is presumedly distributed to several customers. With a BSD style license, the user/client could also close stuff, and that might seem the same, but he’s the only one – on his level – affected. Of course, if he redistributes, he then becomes the vendor and has to decide on his source policy independently. That’s again the Gnu/BSD war, but you have to look on the same vendor/client level to catch me here.

In the former case (dual licensing) the customer knows where he starts, so that’s not really a bait-and-switch. In the latter (dual edition) it’s trickyier, as support might turn out to depend of closed source features. Not good indeed.