Anybody can get moksa

After the completion of ātmā-jñānam, śruti reminds us there is another kind of freedom which one can gain, which is through karma-upāsana-samuccayaḥ (combination of karma and upāsana) which gives krama-mukti (freedom in stages), by gaining brahmaloka.

śatam caikā ca hṛdayasya nāḍyastāsām mūrdhānamabhiniḥsṛtaikā |

tayordhvamāyannamṛtatvameti viṣvaṅṅanyā utkramaṇe bhavanti ||2-3-16||

There are one hundred and one arteries of the heart; of them one has pierced the crown of the head. Going upward by it, a man at death attains immortality. But when his prana passes out by other arteries, going in different directions, then he is reborn in the world.

The result of karma-upāsana-samuccayaḥ is kramamukti (gain moksa by stages) is again told. śatam caikā ca hṛdayasya nāḍyaḥ - there are one hundred and one energy channels of the heart. 101 primary nādī emerge and spread through out the body. tāsām mūrdhānamabhiniḥsṛtaikā - of them, one goes through the middle of the body and extended towards the crown of the head. tayordhvamāyannamṛtatvameti - by that exit, one travels to brahmaloka (relative immortality).The subtle body of the upāsaka (one who does upāsana) will exit through the suṣumṇā nādī, and travel to brahmaloka taking the path called śukla gati. In brahmaloka, upāsaka will get jñāna from brahmaji, and attain moksa. This is called krama-mukti (gaining moksa in stages).

If one performs karma without upāsanā, he will not travel through suṣumṇā nādī, viṣvaṅṅanyā utkramaṇe bhavanti - but his prana passes through other arteries, going in different directions, then he is reborn in the world. The world which he travels to and the nature of his birth will be based upon his karma.

aṅguṣṭhamātraḥ puruṣo'ntarātmā sadā janānām hṛdaye saṃniviṣṭaḥ |

taṃ svāccharīrāt pravṛhenmuñjādiveṣīkām dhairyeṇa tam vidyācchukramamṛtam

tam vidyācchukramamṛtamiti ||2-3-17||

Puruṣa, the ātmā within, is of the size of the thumb. It is ever seated in the heart of

the people. One should separate that from one’s own body with alertness, like

(separating) the stalk from muñjā grass. May one know that ātmā to be pure and

immortal; may one know that ātmā to be pure and immortal – thus (ends the

teaching).

At the end of the Upanisad, śruti comes back to the topic of jīvanmukti as people generally remember the last point of the teaching. The truth of oneself is summarised and re-ascertained once more in this mantra. aṅguṣṭhamātraḥ puruṣo'ntarātmā sadā janānām hṛdaye saṃniviṣṭaḥ - there is one all-pervading puruṣa ever seated in the heart of people as the inner self of all.  Inner self means the real self, where other things which I take to be myself are not the real self.

Therefore, taṃ svāccharīrāt dhairyeṇa - one should separate that real self from the body-mind-sense-complex. This is the discriminative knowledge called ātma-anātma-vivekaḥ. One must be alert in separating ātmā and anātmā just as one would be careful in separating the stalk from the muñjā grass - pravṛhenmuñjādiveṣīkām.

tam vidyācchukramamṛtam -  may one know that ātmā to be pure (free from impurities like kāmā, punya-pāpa, etc.) and immortal (free from life of samsāra).

tam vidyācchukramamṛtamiti - may one know that ātmā to be pure and immortal. This sentence is repeated to indicate the conclusion of yamarāja’s teaching to naciketa.

Next is the last mantra.

mṛtyuproktām naciketo'tha labdhvā vidyāmetām yogavidhim ca kṛtsnam |

brahmaprāpto virajo'bhūd vimṛtyuranyo'pyevam yo vidadhyātmameva ||2-3-18||

Naciketa completely acquired this knowledge along with the method of yoga

which was taught by yamarāja. Thus, having attained brahman, he became pure

and immortal. Anyone else too, who thus knows ātmā, (attains brahman).

This is the conclusion of kathopanisad. It glorifies naciketa, who is a brilliant student who received this knowledge and got liberated. mṛtyuproktām naciketo'tha labdhvā vidyāmetām yogavidhim ca kṛtsnam - naciketa attained this wisdom given by yamarāja who also taught him meditation that is required for the assimilation of the teaching (nididhyāsanam). brahmaprāpto virajo'bhūd vimṛtyuḥ - thus, having attained brahman, he became pure

and immortal. anyo'pyevam yo vidadhyātmameva - anyone else receiving the same wisdom in the same manner will attain brahman and become immortal. Upanisad  ensures that there is no restriction related to position, gender or āśrama to gain brahmajñānam. Such a person will be free from pāpa as well as puṇya. Once karma is not there, there is no rebirth and without birth, there is no death. Therefore, whoever studies kathopanisad will be liberated here and now. This is the phalaśruti given by upanisad.

Om Tat Sat