OpenSource to Commercial Qt?

[Raccoon29]

Hi all,
is it possible to port a source from the open source qt to the commercial one?
I mean, if I have a project that is compilable and works perfectly with the open source library, is it possible to compile the same project upon the commercial library without compatibility error to occurr?
In few words, are open source version and commercial compatible?

[jpn]

Can we use the Open Source Edition while developing our non-opensource application and then purchase commercial licenses when we start to sell it?

[Raccoon29]

Can we use the Open Source Edition while developing our non-opensource application and then purchase commercial licenses when we start to sell it?

Does it mean that if I have developed a project with the open source lib,it is too late, thus I must die?

PS: I looked for the answer but I didn't find that entry, thank you jpn.

[pherthyl]

There's two issues here. One is the legal one which jpn pointed out. You're not allowed to start a project with the open source version of Qt and then buy the commercial version later.

Does it mean that if I have developed a project with the open source lib,it is too late, thus I must die?

My personal feeling is that if you started some experiments with the open source version, but havent released the program yet, and now you want to buy the commercial version for it, then do. You win and trolltech gets another license sale. If you adhere so strictly to the rules then you lose and trolltech loses a sale too.
I know no one is going to agree with me on that point though. Don't take it as an endorsement, I'm just stating a personal opinion.

The other issue is the technical one, and it doesn't exist. The commercial version is 100% compatible with the open source version, so "porting" is just a recompile of your program.

[Raccoon29]

Thank you pherthyl, very exhaustive, exactely all I wished to know

[GreyGeek]

.....

My personal feeling is that if you started some experiments with the open source version, but havent released the program yet, and now you want to buy the commercial version for it, then do. You win and trolltech gets another license sale. If you adhere so strictly to the rules then you lose and trolltech loses a sale too.
....
The commercial version is 100% compatible with the open source version, so "porting" is just a recompile of your program.

Your "personal feeling" is mine also. I use the commercial version of QT at work and on occasions I email the source home to play with the code at night on the GPL version of QT. When I am done I email the results back to work and I have no trouble with the process.

[katrina]

I can't imagine anyone giving you a hard time about using the GPL version at home when you own a commercial license, since its a per-developer and not per-machine license.
As far as starting writing a program using the GPL version then getting a commercial license, I would talk to Trolltech Sales about it, I am pretty sure they would be willing to work something out regarding that (maybe like back-license payments to the time you started writing the application or something along those lines).
(These are, of course, just my personal thoughts on the matter)

[wysota]

My feeling is that:
1. You can always relicence your application, because it is YOUR application so nobody can tell you what licence to choose for it as long as you don't violate any licencing scheme.
2. GPL starts to apply in practice when you start DISTRIBUTING the software so until you do, the software doesn't have to have any licence, so you are not switching from open to closed source - you don't have to publish source code of any application written for personal use.

Beware that this is my personal feeling though - don't rely on it and don't quote it outside this discussion

[Raccoon29]

2. GPL starts to apply in practice when you start DISTRIBUTING the software so until you do, the software doesn't have to have any licence, so you are not switching from open to closed source - you don't have to publish source code of any application written for personal use.

So for "distributing" do you mean give it to some distribution company that sells it on wide range or just sell it to someone, or both, ot what else?

[wysota]

So for "distributing" do you mean give it to some distribution company that sells it on wide range or just sell it to someone, or both, ot what else?

I mean make it available in whatever means possible for people other than the development unit. So in this case "both".