If we don’t use the term “Arabic philosophy” then what single term could contain all three of the men in your example? I don’t think there is one, unless perhaps one said “Middle Eastern Philosophy”, but that’s unnecessarily vague and is based on geography instead of language. I think it’s perfectly reasonable to posit that “Arabic philosophy” is the correct term here, as the Arabic language is the common denominator for all three of the examples you gave:
Ibn Sina/Avicenna: Persian/Muslim who wrote in Arabic (as most Islamic scholars of his time did)
Ibn al-Rawandi: Persian/atheist (I believe he too wrote in Arabic, but correct me if I’m mistaken)
Hunayn ibn Ishaq: Arab/Christian who translated from from other languages into Arabic.
I’m not 100% clear on whether Hunayn ibn Ishaq wrote in Persian or Arabic, but if his writings are in Arabic then are we classifying him based on his ethnicity or by the language in which he composed? If he wrote in Arabic then he too would fall into the “Arabic Philosophy” category. That makes all three of the examples above fall into the “Arabic” category, even though they were ethnically and religiously diverse. So I don’t yet see the problem with the term “Arabic philosophy” to encompass scholars such as these.
It’s important to remember that we’re saying “Arabic” and not “Arab” philosophy: one denotes a language and the other an ethnicity. Since TextKit is based around grouping threads and sections by language, I think it’s unavoidable that “Arabic Philosophy” will be a common term going forward if we wish to create a new Classical Arabic section. Perhaps the term “Arabic-Language Philosophy” would be more precise going forward.
I’d like to see a Persian section develop too, as I saw you also expressed interest in that.