How else do you run programs on Linux? Edit: yes! And it in the general case it get really twisty and interesting. The classic example is a GPL cloning the f

How else do you run programs on Linux? Edit: yes! And it in the general case it get really twisty and interesting. The classic example is a GPL cloning the functionality of a closed source program, down to arguments and options. Now, if you made some sort of closed source plugin for the GPL program, that's OK, if the plugin API was part of the originally cloned program. However, if the plugin API was an innovation in the GPL program, then a proprietary plugin the can easily be infringing. (And as always with GPL, only on distribution.)