Hello Jookia,
How will proprietary Genode distributions use GPLv2 code from Linux or other copyleft projects, or do they just not?
under the commercial license, Genode is an ingredient of a proprietary operating system, let's call it "Vendor OS". The Vendor OS comes with a proprietary system library. The fact that this proprietary system library is somehow based on Genode does not matter. The end user only sees the Vendor OS, not Genode.
So your question can be more generally stated as "Can a proprietary operating use GPL software?". The answer is obviously yes. E.g., before the Linux kernel was born, GNU was primarily running on top of proprietary Unix variants. Also, GPL software runs on top Windows OS or other proprietary OSes.
When shipping a Vendor OS that includes GPL components, the Vendor needs to comply with the GPL licenses of the used components. In particular, the Vendor needs to provide the used GPL source code as well as all the prerequisites that would be needed by the user to reproduce the binary. (e.g., since Vendor OS is based on Genode, the most practical approach for the Vendor to comply with the GPL would be to provide the Genode source code that was used for building the binaries present in Vendor OS)
The interaction of GPL software with proprietary software in general is well understood and documented by the FSF. All the established rules and practices apply to Vendor OS. For example, whereas it would be fine to use the Linux USB driver as a component on Vendor OS as it is a separate program, it would not be possible for a proprietary component to directly use the Linux TCP/IP stack because on Genode, the TCP/IP stack is a library, not a separate program.
Does this explanation answer your question?
Regards Norman