At least the author of QSpice has committed to release the source of all models (including his tweaks for convergence). So you can take the transistors to a different SPICE engine with a simple netlist import.
The touted benefits of QSpsice include better numerical fundamentals, so who knows what happens when you take a tuned model and plug it into a different engine? The way it is described, the improvements to the SPICE engine could be valuable to anyone interested in numerical code and scientific computing, all the more reason why keeping it closed is a shame.