Is there any original manuscript of Dhanurveda or the original text which can be read online.
You can read Dhanurveda from sanskritdocuments.org in Sanskrit in Devanagari and in the transliterated form.
॥ धनुर्वेद ॥
अथ धनुर्वेदः
ईश्वरोक्ताद्धनुर्वेदाद्व्यासस्यापि सुभाषितात् ।
पदान्याकृष्य रचितो ग्रन्थः संक्षेपतो मया ॥ १॥
English translation for that is available at here.
You can get authentic/original scripts with accent (Swara) from vedicreserve:
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Śhiva Dhanur Veda of Maharshi Śhārṅgadhara (Same as mentioned for sanskritdocuments.org)
Nīti Prakāśhika of Maharshi Vaiśhampāyana