I'm not a lawyer and don't like writing sentences with "probability bordering on certainty", etc.
With the current sota models code is free.
- Their output is hyper-customized/optimized for their personal use case, constraints and quirks
- They have zero interest in being an open source contributor and maintainer. Usually because it's a lot of additional work, sometimes for personal safety reasons (harassment targets etc.) In a workplace it can also mean dealing with an extremely tedious legal process with months of uncertainty.
- They figure anyone who wants something similar can just make it themselves instead of using theirs. If I spent between fifteen minutes and two days to make some software, in 3-6 months someone with fewer skills will probably make it in 5 minutes to a few hours using a more powerful model.
- They may not have full rights to redistribute their source code.
Basically most people - individuals and corporations alike - aren't actually interested in donating to open source and in many cases have anti-incentives to do so.