Śrīla Rūpa Gosvāmī is trying here to describe the different achievements of the impersonalists and the personalists. Generally, those who are impersonalists and inimical to the Supreme Personality of Godhead get entrance only into the impersonal Brahman, when and if they reach spiritual perfection. The impersonalist philosophers are in one sense like the enemies of the Lord because the out-and-out enemies of the Lord and the impersonalists are both allowed to enter only into the impersonal effulgence of the brahma-jyoti. So it is to be understood that they are of similar classification. And actually the impersonalists are enemies of God because they cannot tolerate the unparallelled opulence of the Lord. They try always to place themselves on the same level with the Lord. That is due to their envious attitude. Śrī Caitanya Mahāprabhu has proclaimed the impersonalists to be offenders of the Lord. The Lord is so kind, however, that even though they are His enemies, they are still allowed to enter into the spiritual kingdom and remain in the impersonal brahma-jyoti, the undifferentiated light of the absolute.
Sometimes an impersonalist may gradually elevate himself to the personal conception of the Lord. The Bhagavad-gītā confirms this: "After many births and deaths, he who is actually in knowledge surrenders unto Me." By such surrender, an impersonalist can be elevated to the Vaikuṇṭha-loka (spiritual planet) where, as a surrendered soul, he attains bodily features like the Lord.
In the Brahmāṇḍa Purāṇa it is stated: "Those who have achieved liberation from material contamination, and those who are demons and are killed by the Supreme Personality of Godhead, become absorbed in the Brahman concept of life and reside in the spiritual sky of the brahma-jyoti." That spiritual sky is far beyond the material sky, and it is confirmed also in the Bhagavad-gītā that beyond this material sky there is another, eternal sky. The enemies and the impersonalists may be allowed to enter into this Brahman effulgence, but the devotees of Kṛṣṇa are promoted all the way to the spiritual planets. Because the pure devotees have developed their spontaneous love for the Supreme Personality of Godhead, they are allowed to enter into the spiritual planets to enjoy spiritual bliss in association with the Supreme Personality of Godhead.
In the Tenth Canto, 87th Chapter, 19th verse, of Śrīmad-Bhāgavatam, the Vedas personified address the Lord in this way: "My dear Lord, yogīs meditate upon Your localized features, and thus they achieve the spiritual perfection of being merged in the impersonal brahma-jyoti. Persons who treat You as an enemy achieve the same perfection without meditating. The gopīs, who are embraced by Your serpentine hands and who have such lusty attitudes, also achieve the same perfection. And, as far as we are concerned, being different demigods in charge of the different parts of Vedic knowledge, we are always following in the footsteps of the gopīs. Thus we hope to attain the same perfection." By "the same perfection" we must always remember the example of the sun and the sunshine. Those who are impersonalists can merge into the sunshinelike brahma-jyoti, whereas those who are in love with the Supreme Person enter into the supreme abode of the Lord, Goloka Vṛndāvana.
The "lusty attitude" of the gopīs does not refer to any sort of sex indulgence. Śrīla Rūpa Gosvāmī explains that this "lusty desire" refers to the devotee's particular attitude of association with Kṛṣṇa. Every devotee in his perfectional stage has a spontaneous attraction to the Lord. This attraction is sometimes called the "lusty desire" of the devotee. The lust is the devotee's excessive desire to serve the Lord in a particular capacity. Such desire may seem to be a desire for enjoying the Lord, but actually the endeavor is to serve the Lord in that capacity. For example, a devotee may be desiring to associate with the Personality of Godhead as His cowherd friend. He will want to serve the Lord by assisting Him in controlling the cows in the pasturing ground. This may appear to be a desire to enjoy the company of the Lord, but actually it is spontaneous love, serving Him by assisting in managing the transcendental cows.
This extreme desire to serve the Lord is manifest in the transcendental land of Braja. And it is specifically manifested amongst the gopīs. The gopīs' love for Kṛṣṇa is so elevated that for our understanding it is sometimes explained as being "lusty desire."