Theres no bonus so I guess that the market finds a natural equilibrium in price between the two different chains and you exchange them manually as I'm not certain if the ability to burn BLK for the BLN coin lasts forever or not actually.
Bitcoin to a degree can allow it due to the network effect it has and a huge team for marketing and coding .. no other projects should encourage these copy and paste developers to scam investors and supporters to their projects that they could not even maintain on their own steam.
Sounds like an eternal dilemma because theres a few reasons for the code being an open book. But BLN is taking a new direction for itself maybe thats part of it