It may seem a stupid question to ask, but please can you clarify exactly what you mean by “Provided by Xtravirt as an open source solution on a ‘not-forsale’ basis“?
For example could your vPi code be included on a RaspberryPi that is part of a solution being sold on to an end user (or intermediary customer)?
There would be no specific/direct billing for the vPi software itself, but it would be configured as part of the complete solution which is being billed.
I would like to use vPi in a bespoke solution, but I need to fully understand the license terms before I go much further.
Thanks
Martin