Not a lawyer, caveats abound, and all that, but;

Excerpt from GPL's licence FAQ:

The program dynamically links plug-ins, and they make function calls to each other and share data structures, we believe they form a single program, which must be treated as an extension of both the main program and the plug-ins. This means that combination of the GPL-covered plug-in with the non-free main program would violate the GPL.

So, it sounds like either way you're likely to need to release under GPL or find a different library.

http://www.gnu.org/licenses/gpl-faq.html#IfInterpreterIsGPL

On Tue, Apr 16, 2019, 07:36 Richard Frye <richard@codingstudios.com> wrote:

I want to write a program that is for sale without releasing all of the source code. Some of it is fine but parts are proprietary. Does it matter if I dynamically link the rtlsdr library?

-Richard

On Mon, Apr 15, 2019, 8:45 PM Greg Troxel <gdt@lexort.com> wrote:
Richard Frye <richard@codingstudios.com> writes:

> If I write software that uses the rtlsdr library that is already installed
> on the computer, does my software also have to be opensource?

IANAL, TINLA.

rtl-sdr and osmo-sdr both appear to be GNU GPLv2.

The standard interpretation is that if you create a derived work by
writing a program that uses those libraries, then distributing that
derived work requires permission from the copyright holders of the used
libraries. And, that permission is only available if you license your
work under the same license, GPLv2. That is the point of the license.

If you want to write software and not distribute it at all, that's
another matter, and the standard interpetation is that this is ok.

What are you trying to write, and what are you thinking about for
licensing, other than GPLv2?