Yes, it's a community mod and many of developers like you choose to hide their source code wich ends with dead project / buggy things that others can't fork to help fix/improve.
There is absolutely no reason to not opensource mods.
Like CPM that I like but I found the developer reason stupid to not opensource. Just because some kids copy/paste and release mods without credits. Yeah it's a bad, but, you are the main developer and have the community behind you, let these kids doing sh*t and allow others developers to help / fork with new features or performances improvement.