[cyraxjoe]

If you modify some free software, repackage and resell it without contributing the changes, then you are breaking the intentional viral effects of the license.

Most of the web stuff that people work on these days is rather outside of this problem, unless is an AGPL license.

It is tricky if you want to base your commercial product on a derivation of a GPL licensed software.

[rini17]

Not really, GPL only says whoever receives binaries, must also receive their source code. Receiver then can, but is not obliged to, publish it or contribute back. Still, yes it does cause problem with various licensing schemes.

But per-copy licensing without source code availability is an atrocity enabled only by misapplication of copyright/IP laws, where copyright holder can write practically anything into the EULA and have the law system enforce the terms "for free". I hope our civilization eventually comes up with better and more GPL-aligned software distribution model.

[bkor]

You don't have to contribute GPL changes back. Whomever you give a binary to you'll have to give the source to if they ask. It's pretty much that simple.

[xenadu02]

That's a distinction without a difference as anyone who receives the binary must also have access to the source and be free to redistribute that source, so effectively all derivative works of GPL'd code are GPL'd unless you refuse to distribute.