Using kompozer-0.8_beta3.ebuild, I get the following error:

...
 * kompozer-0.8b3-src.tar.bz2 RMD160 SHA1 SHA256 size ;-)                                                          [ ok ]
>>> Downloading 'http://kompozer.sourceforge.net/l10n/myspell/myspell-dict.en-US.xpi'
--2010-09-06 15:39:07--  http://kompozer.sourceforge.net/l10n/myspell/myspell-dict.en-US.xpi
Resolving kompozer.sourceforge.net... 216.34.181.96
Connecting to kompozer.sourceforge.net|216.34.181.96|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 249556 (244K) [application/octet-stream]
Saving to: `/usr/portage/distfiles/myspell-dict-en-US.xpi'

...
>>> Unpacking myspell-dict-en-US.xpi to /var/tmp/portage/app-editors/kompozer-0.8_beta3/work
unpack myspell-dict-en-US.xpi: file format not recognized. Ignoring.

...
>>> Configuring source in /var/tmp/portage/app-editors/kompozer-0.8_beta3/work/mozilla ...

==========================================================
Building kompozer-0.8_beta3 with the following configuration
    --enable-application=composer   mozilla.org default
    --enable-optimize               mozilla.org default
    --disable-debug                 mozilla.org default
    --enable-xpfe-components        mozilla.org default
    --disable-tests                 mozilla.org default
    --disable-installer             mozilla.org default
 * ERROR: app-editors/kompozer-0.8_beta3 failed:
 *   error reading mozconfig: ac_add_options --enable-extensions="default spellcheck"