[Logician]

not tested but should work:

Find:
---
function getforumrules($foruminfo,$permissions) {
// array of foruminfo and permissions for this forum
global $offtext,$ontext,$forumrules,$session;
---

Replace it AS:
---
function getforumrules($foruminfo,$permissions) {
// array of foruminfo and permissions for this forum
global $offtext,$ontext,$forumrules,$session, $styleid;
---

Find:
----
$notword = 'not';
----

Replace it AS:
---
if ($styleid==X) {$notword = 'whateeveryouwordis';}
else {$notword = 'not';}
---

Substitute X with your non-english style's id..

Enjoy..

Logician