Without knowing anything I wrote a big application, almost 1 year coding. It does Video/Audio such as softphone for commercial use (we sell it). I used a framework which was licensed under the LGPL, ...
I thought LGPL was a permissive license, just like MIT, BSD or Apache. But today I read, that only linking to LGPL (libraries etc) is allowed from closed-source code - other than that, it's copyleft - ...