Documentation System Comparison

-	Cross-Ref Between Classes	JavaDoc Syntax	Understands Inheritance	Overview Docs	Localised	GUI	License	Cross Platform
Acid	?
ASDocGen	?
FlashDocsGen	?
as2api	yes	yes	yes	no	no	no/yes ¹⁾	GPL	yes
Natural Docs	no	yes ²⁾	no	yes	no	no/yes ³⁾	GPL	yes
ActionDoc	?
ZenDoc	no	yes	no	no	no	yes ⁴⁾	GPL	yes

Cross-Ref Between Classes This means that when one class's API uses another class' (for instance, as the return type of a method) the API reference includes a hyperlink to the referenced class.
JavaDoc Syntax Does the tool support the JavaDoc syntax? This could be seen as an advantage (since it's relatively standard) or a disadvantage (if you think the syntax is ugly.)
Understands Inheritance When documenting the API of a class, is information about any superclass' API included as appropriate?
Overview Docs Any tool in this list must allow documentation to be attached to classes, methods, fields, etc., but does the tool also allow documentation to be attached to each package, and to the whole library of code?
Localised Does the tool include specific features to support generation of documentation in different (human) languages?
GUI Does the tool come with a GUI? (If 'no', it's a command-line tool.)
License What license is the software made available under?
Cross Platform Does the tool run on several operating systems (Windows, OSX, Linux)?

¹⁾ FlashDevelop includes a standalone GUI (Windows) for as2api

²⁾ Natural Docs is compatible with JavaDoc syntax but also has its own syntax.

³⁾ Natural Docs has a number of third-party GUI tools available.

⁴⁾ ZenDoc uses a web-based interface but can also be run from the command line.