[DonaldFisk]

I don't see any way of legally enforcing payment for the use of software released under the terms of the GNU GPL. Points 2 and 3 have the risk of being undercut, though they might work in some cases. Point 4 might be valid, but once its released there's no further guarantee you'll be paid.

I've thought about licensing issues, as I have software I'd like to release when it's ready, but I also would like to be paid for it by anyone who uses it to generate revenue for themselves.

Up until the early 1980s, system software development was paid for by various computer manufacturers, as it could only run on their machines. As a result of generic hardware and open-source software, hardly any similar work exists today.

[nickpsecurity]

In a similar discussion, someone working for OpenSUSE pointed out that their business model is selling FOSS. They make about $20+ million a year. Red Hat even more despite the fact that CentOS is basically Red Hat for free. You have a potential advantage in the enterprise market where companies are hesitant to take free software since they want someone to be responsible for it. They'll pay you for GPL stuff if they can call you for improvements or fixes.

[JoshTriplett]

For the first point, it applies when releasing code other people will want to link to, such that the GPL would apply. It doesn't help with a standalone program that nobody wants to build on or derive from; you'd need the other cases for that.