i don't agree with you brother, the site is really nice apart from the translation, and i didn't bother to look at it, because what i liked was the simple syntactical analysis specially the treebank.
Please note that it is Makruh Tahrimi (highly disliked and close to being haraam) for the 'awaam (general lay people) to read the books written by innovators (Ahl ul Bid'ah).
yes, if you learn aqidah, hadith, tafsir or other uloom, but there is nothing wrong in learning a language. knowledge is the lost treasure of muslim, wherever he finds it he is more deserving it
عَنْ أَبِي هُرَيْرَةَ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ الْكَلِمَةُ الْحِكْمَةُ ضَالَّةُ الْمُؤْمِنِ فَحَيْثُ وَجَدَهَا فَهُوَ أَحَقُّ بِهَا
سنن الترمذي كتاب العلم باب ما جاء في فضل الفقه على العبادة
with regards to creed, hadith, tafsir, it is certainly very dangerous, but i don't think that your stated fatwa apply to learning a language, otherwise you shouldn't send your children to english schools, or attend language classes abroad just to make your living (i assume english is not your mother tongue)
you should also advise that our dars e nizam texts should not be taught from deobandi publications, no dar al-uloom teaches every book entirely, students have to read them by themselves so the perils of misguidance are there as well, and even more than a language course.
sorry, but i am quite comfortable with it while i am fully aware of the perils of learning from ahl al-bidah.