why is taking open-source code closed expensive?

[Rick Moen]

Quoting Joseph Hick (leet16y at yahoo.com):

> from http://www.catb.org/~esr/Licensing-HOWTO.html#id2790430

> i didn't understand why taking open-source code and keeping it closed
> is expensive?

The canonical answer, before they collapsed and were bought up by Wind
River, used to be "Ask BSDi."  ;->  

If you fork an open-source codebase and maintain your fork separately as
proprietary code, you are cutting yourself off from most of the benefit
of the collaborative, open development process.  Costs of coding and QA
rise, accordingly.

> "Are copyleft licenses enforceable? We believe they are, but there
> hasn't been a court test yet. There are some promising precedents in
> case law pertaining to shrink-wrap licenses"
> 
> if we are not sure that licenses like GPL v3 are enforceable under law
> then how do so many programmers take the risk of releasing their
> project under GPL v3.? :-O

There wasn't caselaw about copyleft licence enforceability when that
HOWTO draft was released, but there has been in the interval.

(I'm guessing you meant to say "GPLv2", above.  GPLv3 being only days
old, the amount of software under it specifically so far is necessarily
modest.)