I wouldn't describe myself as a chess engine developer - more a nnue trainer. Let me tell you a bit where I come from: Apart from nodchip, a user by the name of 'Gekkehenker' and me were the first 2 persons to ever train nnue nets for Chess (if we don't count Shogi as chess). We openly shared our data with everyone, found out better parameters and eventually beat Stockfish master.
Without collaboration it wouldn't have been possible. We helped other people and tried various net sizes and architectures. I firmly believe that the set of data you use doesn't matter too much if, and only if, you have a uniquely built neural net topology. This is the case in Stockfish, since Sopel came up with halfkaV2 specifically for Stockfish and nobody else uses it.
Of course the nets we produce are available to everybody which is great. And if you don't have a unique NN implementation and refine your data then that's great too. We want to find out new things that help the chess engine world.
Basing one's search on an engine somebody else has done and coupling that with a net trained by and for the very engine you took code from isn't exactly helping anybody in terms of ideas. The same is true for changing the net size and marketing it as a big innovation. Of course you can work on top of open source engines - nothing bad about that.
The thing that upsets me that it took years for some authors to admit that their work is a derivative of other open source engines.