I'm creating a software application where up until now, the majority of code and assets have been produced by me. There are smaller bits of code that I've taken from other places; these have all been licensed as "do what you want with it". I've gotten to a point however, where I want to incorporate fairly large parts of another project in mine, and this other project is licensed with GPLv3.
I hadn't considered licensing issues with my software up until this point; as of right now it's just sitting on my machine with no official license.
Incorporating this other project in mine would require me to adopt the GPLv3 license as well. I decided that while I'm okay with most of what I've written to be licensed under GPL, I want some of what I've written to be available for proprietary derivative works (which is incompatible GPL).
So how do I get around this? What I've come up with so far is using "plugins" or add-ons for my app. While the base application is GPL, I can license the code I want for derivative works to be LGPL or even closed, and simply have them be plugins for my GPL app. Is this viable? My argument is that a plugin is simply something that adds functionality, and does not make my base application a derivative work of the plugin.