Violates the GPL most open source software is published under.
Perhaps. But once BobCo makes its in-house changes to its version of open-source ... which it's perfectly free to do ... then it has assumed a monetary stake in the outcome. The Open Source model does not account for that.
Why are we even talking about the GPL on this thread? Mozilla.org publishes software under the Mozilla Public License, which is a bit more commercial-friendly.