[distances]

Qt-as-the-company has always made it very clear that you can't switch your Qt LGPL/GPL project to a commercial one if you didn't start with the commercial Qt license from the beginning.

You're right, it does sound a bit nasty. No, I haven't read the license myself. It's been brought up multiple times on official Qt blog comments and mailing lists, though.

Edit: checked it now, and it's clearly written at https://www.qt.io/faq/, "Developing with a Commercial License":

> Q: If I have started development of a project using the open source version (LGPL), can I later purchase a commercial version of Qt and move my code under that license?

> A: This is not permitted without written consent from The Qt Company. If you have already started the development with an open-source version of Qt, please contact The Qt Company to resolve the issue.

[joezydeco]

It's not standard and it's not pleasant to most ears, but I think over the last 20 (!) years of development the Trolltech guys have tried to make sure they could advance Qt and make a living doing it. I respect that a lot.

OSS was a completely different animal back when this thing started. And it was forward thinking to avoid the whole problem with people demanding free support and bugfixes for open-source code.

[distances]

Not saying that this is wrong, just that it's no wonder if they think this to be FUD if one isn't familiar with the rule.

As for the reasoning, a customer developing their product for years in-house and switching to commercial just before releasing would definitely place Qt financing in a shaky ground when compared to traditional commercial frameworks.

[Dlotan]

At my last company we had this situation. But they are more than happy to sort this out for free if you take a license for the next 2 years.

[distances]

Good to hear!

[mjevans]

It would be nice if they had some form of migration publicly stated. For example something like this:

If your project decides to go commercial the initial license term will include a cost of conversion based on the quantity of code already written.

It would be interesting if they expressed that rate as something like:

A gz -1 compressed tarball of the affected source code will be created, the size (in bytes) multiplied by X is the maximum fee we would charge for retroactive licensing.

I choose the wording 'maximum' there as it still allows them to offer better deals under other circumstances.

[cplease]

I imagine they have sales guys. If you have a meaningful amount of money to spend they will talk to you. If not, don't use their LGPL code in a proprietary product.

Qt is not an end-user, boxed product. This may shock you, but B2B software doesn't always have a public, standard price list.

[mjevans]

Shock, no; sadden and drive me to other ventures yes.

My rule of thumb for pricing is that if someplace /makes you ask/ they aren't going to sell at a price you'd find worthwhile.

[cplease]

And their rule of thumb is that you aren't worth the sale. Bespoke software is not a bulk commodity. They have a free product. If you're going to be a cheapskate, use it.

The notion of charging by byte, as if software were content farming, shows that you are obviously not a professional.