HMD Global published the kernel source code for the newly announced Nokia 1 Plus. Under the GPL, LGPL or any other type of license for the open source code HMD is using, the company is obligated to provide the changes they made to the public. For that purpose, Nokia Mobile has a dedicated site Nokia.com/phones/opensource, where all the source codes should be posted.
At the moment, the source code for Nokia 2, Nokia 3.1 Plus and the newly launched Nokia 3.2, 4.2 and 9 PureView are missing. As well as for the 8110 4G, that should also be included because KaiOS is built on an open source platform.
For regular users, source codes don’t mean anything, but for the dev community it might, if HMD Global offered bootloader unlock for more devices. It’s also a matter of law, so they have to share it.