Hi, I am looking for web-based Bookmark Management software.  I am
specifically looking for software to run on my own website, not a
service that I would access on someone else's website.  Also, I am not
interested in client software such as Windows programs, browser
plug-ins, etc.

For example, this list looks like the type of software I'm looking
for: http://www.linuxlinks.com/Web/Utilities/Bookmark_Manager/. 
Whereas this list looks like mostly hosted services, which I am not
interested in: http://directory.google.com/Top/Computers/Internet/On_the_Web/Web_Applications/Bookmark_Managers/?tc=1/.

I'm posting this question to get some help in narrowing down the
options.  The ideal answer would give me a "Top 3" (or so) list of
software to choose from, including the reasons that you chose those as
the best options, and the pros and cons of each.  Ideally you would be
able to find published comparative reviews, but if not then you can
rely on the information published on the developers' websites.

My requirements are:
1. Software must be written in PHP
2. Must store data in a MySQL database
3. Must be open source
4. Must be stable (non-Beta)
5. Must not require any client software installation (cannot require
client-side Java or ActiveX etc)
6. Must be usable from current versions of IE and Mozilla (no support
for older browsers is required)
7. Must have these features:
7a) Organize bookmarks in categories
7b) Categories can be stored within other categories
7c) Each bookmark can have a title, a URL, and optional comments (a
few words to a few sentences)
7d) Add / update / delete category or item
7e) (optional but desired) Ability to segment bookmarks into public and private

Given these requirements, the following evaluation criteria will
decide which software is "better":
1. Being actively maintained by the developer(s)
2. A large number of installations and active user community
3. Good documentation
4. Beyond that, the decision will come down to factors like ease of
use, productivity, flexibility, etc.