how much right do I have on my project, if there are patches by others?

[Rick Moen]

Quoting Matthew Flaschen (matthew.flaschen at gatech.edu):

> It would seem that any interpretation except a series of independent
> (i.e. neither joint nor collective) derivative works...

[USA law assumed for present discussion.]

A third-party patch in _separate_ form is indeed logically treated as
commentary; thus, as an independent work.  Merging it into the original
work strikes me as very likely to create a derivative work -- which then
necessarily falls into either the joint- or collective-work category.

> ...would undermine copyleft.

Doubt it (not that copyright law has a mandate to bolster copyleft).
See below.

> If programs are collective works, the primary author can
> relicense contributions (without explicit copyright assignment) to a
> copyleft program under a proprietary license.

If contributors prove that ye olde primary author has failed to
safeguard their interests or has violated agreements with them, then
nonetheless the primary author may find he/she lacks that option.
Please note that courts tend to measure "interests" for civil-law
purposes in economic terms:  A mere "Hey, your relicensing sucks" isn't
a really promising foundation for litigation.

But, anyhow, in that hypothetical, any party (obviously) can fork
rev. n-1, taking over maintenance under copyleft.

-- 
Cheers,                                      "Reality is not optional."
Rick Moen                                             -- Thomas Sowell
rick at linuxmafia.com