| > The difference is that with the BSDs everyone can take and don't bother to contribute upstream, e.g. Apple and Sony. This depends on the use case of the company. A lot of companies learned that simply forking the project and not giving back is a good pathway to pain because now you have to carry your internal patches forward, as well as a larger and larger diff against the base OS itself as it changes. If you forked (e.g.) FreeBSD 9 and based your product off of it, and the project is now at version 12.x (with 13.x in 2021Q1), then that's a lot to keep up with internally. It's better to use the base OS, and the documented APIs, for one's secret sauce, and give back everything else. This is what vendors like Netflix, Dell-EMC Isilon, NetApp, etc. do. You'll also see quite a few patches from Microsoft and Amazon as they want to sell their cloud services for as many guest OSes as possible. Hardware vendors (Chelsio, Mellanox, Cavium) also throw in support so that hardware companies will use their products with-in appliances. Others, like Sony with the PS4 and PS5, mostly seem to operate in user land and so do not do much kernel-level stuff (except perhaps booting code) that would need to be back ported. |