śrīmān uddhava-dāso ‘pi candrāveśāvatārakaḥ

Uddhava Dāsa is an āveśa avatāra of the Moon-god. (Gaura-gaṇoddeśa-dīpikā 192)

In the Caitanya Caritāmṛta (1.12.83), it is said that Uddhava Dāsa is a branch of Gadādhara Paṇḍita Gosvāmī. As such, he is mentioned by Yadunātha Dāsa, a disciple of Gadādhara Paṇḍita, in the Śākhā-nirṇayāmṛta (35):

ati-dīnajane pūrṇa-prema-vitta-pradāyakam
śrīmad-uddhava-dāsākhyaṁ vande ‘haṁ guṇa-śālinam

I venerate the highly virtuous Uddhava Dāsa, who gave the wealth of love to those who were most fallen.

When Rūpa Gosvāmī was old and living in Vṛndāvana, he was desperate to see Mādhavendra Purī’s Gopāla deity, but unable to go to Govardhana because of his advanced years. At this time, Gopāla came to stay in Mathura at the house of Bitthalnath, the youngest son of Vallabhācārya, ostensibly out of fear of possible attacks by the Muslim iconoclasts. Rūpa Gosvāmī thus had the opportunity to take His darśana. Uddhava Dāsa was amongst the devotees who stayed with Rūpa Gosvāmī at Bitthalnath’s house for an entire month on this occasion. (Caitanya Caritāmṛta 2.18.51, Bhakti-ratnākara 5.1333)

Uddhava Dāsa lived in Vṛndāvana. When Śrīnivāsa Ācārya and Rāghava Gosvāmī were touring Vraja-dhāma, they came to his cottage. He greeted them with enthusiastic hospitality. Uddhava Dāsa was amongst the devotees who bade farewell to Śrīnivāsa Ācārya, Narottama Dāsa Ṭhākura and Śyāmānanda Prabhu as they set off to Bengal with the books that Jīva Gosvāmī had given them. (Bhakti-ratnākara 6.514)

According to the Gauḍīya Vaiṣṇava Abhidhāna, there are two more devotees named Uddhava Dāsa. One was a follower of Sanātana Gosvāmī who performed bhajana in Nandagaon on the banks of Pāvana Sarovara; another was an initiated disciple of Rādhā Mohan Ṭhākura who was a famous poet. He lived in Murshidabad district in the village of Teyagram. His real name was Kṛṣṇa Kānta Majumdāra.