Without the ability to adapt the software to different
devices or
applications, or fix errors (or pay someone to do that), the software
is crippled in its usefulness.
True; buy a licence which includes sources and the right to change it.
That's it.
When buying electronic appliances, at one time you
could rely on the
schematics being in the inside. That meant you could make full use
of the appliance, adapt it to different problems (using a radio as a
guitar amplifier), repair it and keep it in working order, and you
could take it to service men of your choice to have it adapted or
fixed.
But you have to pay an extra fee to get the circuit plans. So if you
want to get the source of proprietary software, you have to pay for it,
too. At least theoretically.
Best regards
ce