The Wayback Machine - https://web.archive.org/web/20111208181846/http://paperlined.org:80/apps/autohotkey/autoit_and_autohotkey.html
an AutoIt / AutoHotkey comparison
AutoIt was first released in 1999. AutoHotkey forked from AutoIt in November 2003 because AutoIt at the time didn't have the ability to have hotkeys, Chris wanted them, and Jon thought it might not be an important feature. Some time after the fork, AutoIt went closed-source.
AutoHotkey is thought to have less memory overhead than AutoIt. While I don't know of any thorough examinations that back this claim up,
AutoIt/AutoHotkey do mirror the Opera/Firefox relationship somewhat (in that
Opera tries to be trimmed-down and fast, while Firefox tries to be able to do everything
under the sun, especially by having a large percentage of its functionality being
implemented within its scripting-language, rather than in C-code).
AutoHotkey is open-source (GPL). AutoIt defies simple classification. Essentially, key parts will always be closed-source to retain control over the project, but the maintainers definitely go out of their way to foster a community of developers.
AutoIt was originally GPL, and was GPL at the time that AutoHotkey forked, but closed its C source due to tensions related to the forking.
The last version of AutoIt that was GPL is still available (see autoit-v3.1.0-src.exehere. Note that none of the files labelled autoit-docs-... are core C source). Even after this version though, some developers were able to submit patches based on the old code (though, of course, they had to be upmerged, which grows ever more difficult as time passes, so that's probably not possible now)
There are a number of ways that AutoIt can be extended or contributed to. Since these allow third-party devs to accomplish most (but not all) of what they might want to do, AutoIt maintainers are less likely to want to go back to open-source.
the Include\ directory (called UDF's, user defined functions) is large and has all the source code visible, and the community can make updates to them
AutoItX is the AutoIt engine inside an ActiveX wrapper, allowing the functionality to be embedded inside other's programs. It has even allowed MoveIt to be created, which allows Lua scripts to be used instead of AutoIt's scripting language.
nascent plugins allow third-party C code to be called from a nice AutoIt-script interface
It's not clear what the license the UDF code is available under, since all the code is visible, and many individual users contributed to them. If the license on those isn't explicitely stated somewhere though, it would default to the project-wide license, which says that it's standard copyright controlled by the core dev team.
Various objective (but imperfect) metrics give mixed indications about whether one is more popular, though those backing AutoIt are probably better trusted on the whole than those backing AutoHotkey.
metrics that indicate AutoIt is more popular
registered forum members (28k vs 8k, though this is lifetime-cummulative, and not indicative even of popularity over the last year)
