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Comment by EStudley | Hacker News Reader

It's a shame I'll never get to use features past Qt 5.4 after their insistence on LGPLv3 and royalties per device sold..

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What suggestion would you make for them to be able to make a living off of open source software?

EDIT: also, it's LGPL or $80/developer-month, not and. I don't see anything about royalties. And considering the GPL doesn't apply until you start distributing the software, you don't need to spend that money during development. You can wait to license when you release and start getting revenue.

I don't know whether this has changed, but they used to forbid you from developing with the open source edition and then releasing under a commercial licence. (They did this with a term in the commercial licence that specified that it couldn't be used with code previously developed with the open source edition.)

This was quite a confusing policy in some ways. I think in practice they expected to resolve such situations by backdating payments for the commercial licence to cover the development period.

(Edit: from https://www.qt.io/faq/#_Toc_3_13 it looks like the policy is unchanged but the wording around it has been softened a bit to encourage negotiation)

3.13 (and 3.12) sounds primarily for avoiding that a company has 30 developers with only the 1 developer (or CI bot) that does the release having a Qt commercial license.

Or that you develop for 12 months and get a commercial license the last month,, when its going to be released.

That is the license terms, but so long as you haven't distributed it before you go to sales and explain the situation they are willing to come to an agreement. Probably this means you pay for all the license term you should have. Something to that effect is even on their pages if you dig around.

The important part is once you realize you have the wrong license you contact sales admit your mistake and make a good faith effort to correct things.

I don't see anything about royalties.

That's for Qt for Devices. Conditions aren't public, but: "To learn about Qt for Device Creation pricing – developer licenses and embedded device distribution fees – start the conversation now"

also, it's LGPL or $80/developer-month, not and.

It's actually more like $300/dev/month unless you qualify as a startup.

Royalties are way high compared to some of the other mature commercial toolkits out there (like Altia or VAPS).

Last time we quoted for our smallish product (1-2K EAU), Qt wanted $5 or $6/unit, purchased in blocks of 1,000 licenses at a time. That was too much of a hit on our BOM, so we went LGPL and haven't looked back.

Is there a good explanation somewhere as to what someone can and cannot make/sell/open/close with Qt? Last I saw, platforms that allow precompiled dynamically-linked libraries (i.e. everything but iOS) could have the LGPL stuff in a separate binary file. But if you linked the code in directly, you couldn't distribute your application without the source.

I wish there was a FAQ with easy answers like "If you write an iOS app with Qt, you can close the source if you pay us a license fee" or something along that line.

IIRC, Xamarin had similar problems, but that went away when they were purchased.

> you couldn't distribute your application without the source.

No, only "re-link-ability" is required, thus you can dump only obj files somewhere.

They don't make FAQ about this, because they don't want to publicly state that it is possible to use free Qt for commercial mobile apps.

Turns out they do have a FAQ about this: https://www.qt.io/faq/#_Toc_3_12

It suggests that LGPL + iOS app store is not OK, but doesn't fully explore why not.

That is because in the iOS app store, Apple is distributing the app. And they are not willing to obey the obligations of the (L)GPL regarding offering the recipients the source code they have the right so. So Apple has banned code with such licenses from the appstore.

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