[onion2k]

I can't see more commercially-oriented paper/website open-sourcing any of their code, even if it's a (good imho) recruitment ploy.

There's very little cost to opening it up, and a huge benefit (recruitment as you say, openness, community engagement, maybe even bug fixes..). Why not open up the code?

[thecatspaw]

opening up publishes all your vulnerabilities, bugs, hacks and swearwords in the code as well. Thats plenty of reasons to not go open source

[Operyl]

Security by obscurity really isn’t a great place to stay on long term. There is also an entire backend to this. I can only see great positives long term here, even if it means someone nefarious finds a bug in the short term.

[onion2k]

Those are reasons to open the code up. You'll be motivated to improve it.