I found about VSCP (www.vscp.org) in the Twitter and just start reading its specification and documentation.
VSCP is a control protocol developed by Åke Hedman since 2000, then it is about 15 years old! Many people are using it for home automation: http://www.vscp.org/wiki/doku.php/who_why_where/the_vscp_team.
The source code is released as GPL/LGPL but has some modified clauses that let users to use it in a “non-viral” mode. You just need to release the modifications you did (if you did it) in the VSCP code. This is similar to FreeRTOS GPL license in this sense.
It is a surprise to know that 8devices USB2CAN dongle has a VSCP driver:
The 8Devices owner is a nice guy, even the USB2CAN schematic is released: