Hence, it is correct that dharma can be directly perceived. In the same way, it is also inferable. Since there is no distinction among the visible causes of service (sevā), learning (adhyayana), etc., no difference of fruit (phala) can be seized without a further condition (nimitta, that is, dharma). Therefore, in this way, since the dharma is directly perceivable and inferable, like it [occurs] in the case of Ayurveda and of politics (arthaśāstra) [whose texts are composed by human authors], also a human sacred text (āgama) [would] be possible (or: "in regard to the dharma, which is cognizable through direct perception and inference, a human text would also be possible, just like politics and medecine [in regard to artha]"). Hence, if through these instruments of knowledge (why plural? does it entail human communication too?) the object of a prescription (codanā, as in MS 1.1.2) could be ascertained as dharma, then prescriptions seizable only through much effort (āyāsa) (that is, the Vedic prescriptions, requiring hermeneutic efforts) would be fruitless. And the interpretation [of MS 1.1.2] as stating that “only the prescription” [is a means of knowing dharma] would not be suitable. If (atha) a certain meaning, not stated by a prescription [and] not contradicted by it [would be dharma], then there would not be anymore the thesis that “only the prescription” [is a means of knowing dharma]. If, on the other hand, a certain [meaning] opposed to the [prescription], like that taught by the Buddha, etc., [could be dharma], then also the interpretation (avadhāraṇa) [of MS 1.1.2] as “the prescription is an instrument [for knowing dharma]” would not be suitable, because it (prescription) would be contradicted.
Hence in all cases the [sūtra 1.1.2] “Dharma is a meaning having a Vedic prescription as its instrument of knowedge” (I am following here Vedānta Deśika's interpretation of this sūtra) would be improper (durvaca).
(This translation has partly been discussed with Marion Rastelli)
I am not sure about the sentence on service. To me, it seems to mean that one undertakes service to God, and study, out of similar reasons (being a Brahman, being born in India…). Service to God would not lead to a super-natural result if it were not for an additional reason (dharma, understood as bhaktidharma).