Hoi Gerard,
it is indeed a huge improvement that finally the source code was made available. This has not yet came to my sight. So GPL violation does not count here.
Anyway, it took a long time to actually become free. When we were trying to work with Linterweb it took us months to get some patches of the code they took from us, and the patches were actually not usable.
Concerning proprietary format: Zeno was kind of proprietary, but at least it existed some documentation and DirectMedia was willing to answer questions. ZIM is completely open and freely documented, so if you don't like our implementation or you think that C++ is not the language of your choice - feel free and go ahead with your own implementation. As long as you follow the standard!
Of course the file format is not fixed until good right now, so if you have suggestions you could name them on the openZIM mailinglist or file a bug at the openZIM website.
What Linterweb did was just changing random thing without documentation and very bad communication towards the openZIM project team. So I do consider it as proprietary - as it is incompatible with both ZIM and Zeno and there is no willingnes to collaborate to fix this issue.
Both Tommi (the openZIM main developer who has also delivered his Zeno-related code to Linterweb) and Emmanuel (from whom they took Kiwix to make it Okawix) have a long story to tell about this. As well as I have, because I am being addressed regularly by Linterweb as they still try to get code and support, but never really get into the project by telling us what they really want and how we could integrate that into openZIM.
We had a Wikipedia Offline meeting in Buenos Aires and someone named Linterweb. Surprisingly for me they are also quite wellknown to the foundation and more surprisingly they have quite similar views as we have.
I would love to see them using ZIM in Okawix, even if it would require some changes if they feel we had to make it more usable for them (even though I see currently no reason why it was not perfectly usable right now). Of course we invited Linterweb to our first developers meeting and two people from them actually registered (one of them was Pascal Martin, the CEO) so we book rooms for them from our project's budget, but they never showed up. A side story though, but it is an excellent example how collaboration with Linterweb is going on.
Regards,
Manuel