GPL and LGPL FAQ quotes

The GPL does not require you to release your modified version, or any part
of it. You are free to make modifications and use them privately, without
ever releasing them. This applies to organizations (including companies),
too; an organization can make a modified version and use it internally
without ever releasing it outside the organization.

But if you release the modified version to the public in some way, the GPL
requires you to make the modified source code available to the program's
users, under the GPL.

Thus, the GPL gives permission to release the modified program in certain
ways, and not in other ways; but the decision of whether to release it is up
to you.

No. The GPL gives a person permission to make and redistribute copies of the
program if and when that person chooses to do so. That person also has the
right not to choose to redistribute the program.

If you choose to provide source through a written offer, then anybody who
requests the source from you is entitled to receive it.

If you commercially distribute binaries not accompanied with source code,
the GPL says you must provide a written offer to distribute the source code
later. When users non-commercially redistribute the binaries they received
from you, they must pass along a copy of this written offer. This means that
people who did not get the binaries directly from you can still receive
copies of the source code, along with the written offer.

The reason we require the offer to be valid for any third party is so that
people who receive the binaries indirectly in that way can order the source
code from you.

Section 2 says that modified versions you distribute must be licensed to all
third parties under the GPL. “All third parties” means absolutely
everyone—but this does not require you to do anything physically for them.
It only means they have a license from you, under the GPL, for your version.