Yeah, some time ago all instances of the word "dueler" were changed to "dueller" in accordance with the British spelling of the word, and I believe several other words underwent such changes. However, American English is still present in a few cases ("labor" and "vigor" come to mind). Unsalable is an alternate spelling of unsaleable, and unsellable means the exact same thing, but is probably less common.
The most correct word would probably be "Unsaleable". If you really think it needs changing, feel free to post in the
Typos, Bad Translations and Text Errors thread.
Sly has already answered the initial question, so we don't need any more discussion regarding translations in this thread.