On 17/08/12 08:55, Russel Winder wrote:
Can I suggest a re-phasing "proprietary code needs to dynamically link to Qt to comply with the LGPL". To avoid the LGPL with Qt you need to buy a commercial Qt licence.
I think this is over-stating the licence requirements. The legally safest option is certainly to dynamically link against the LGPL-licensed code, but it's not an explicitly-stated _requirement_ of the licence.
The requirements are that the recipient of the program must be able to link it to a newer version of the LGPL-licensed part. That could be achieved through dynamic linking, or it could be achieved through distributing object files along with the program. (You could also distribute source code, but since this is what's trying to be avoided here it's not a solution.)
Qt recommends dynamic linking because it can't be guaranteed that some legal jurisdictions wouldn't interpret a statically-linked program as a "derivative work" of the LGPL-licensed code, thus falling under its copyleft provisions. However, such an interpretation is almost certainly not in line with the licence's intentions.
It might be worth contacting the Software Freedom Law Center for advice on these points: https://www.softwarefreedom.org/
