ਸੇਈ ਤੁਧੁਨੋ ਗਾਵਹਿ ਜੋ ਤੁਧੁ ਭਾਵਨਿ ਰਤੇ ਤੇਰੇ ਭਗਤ ਰਸਾਲੇ ॥ ਹੋਰਿ ਕੇਤੇ ਗਾਵਨਿ ਸੇ ਮੈ ਚਿਤਿ ਨ ਆਵਨਿ ਨਾਨਕੁ ਕਿਆ ਵੀਚਾਰੇ ॥
How do you see this line of Page 6 ?
Is it true that Only those people sings "GOD's" praise whom the "GOD' itself likes ?
I am not a scholar, or even a pleasure seeker, not any more, I live life with all its pleasure and its pain, and it all adds up to life, all of it, however, I will try my best to answer your question,
first, taking one liners from the SGGS is in my consideration bad practice, it is akin to taking one line from a famous speech and dwelling on it and ignoring the rest of the speech, to do so to Kennedy or Luther King would take away the very essence of the speech. Also let us not forget that the translator has translated this in the style of the Christian Bible, and also put his own personal spin and understanding on it, but nevertheless
सो दरु केहा सो घरु केहा जितु बहि सरब समाले ॥
So ḏar kehā so gẖar kehā jiṯ bahi sarab samāle.
Where is that Gate, and where is that Dwelling, in which You sit and take care of all?
ਵਾਜੇ ਨਾਦ ਅਨੇਕ ਅਸੰਖਾ ਕੇਤੇ ਵਾਵਣਹਾਰੇ ॥
वाजे नाद अनेक असंखा केते वावणहारे ॥
vāje nāḏ anek asankẖā keṯe vāvaṇhāre.
The Sound-current of the Naad vibrates there, and countless musicians play on all sorts of instruments there.
ਕੇਤੇ ਰਾਗ ਪਰੀ ਸਿਉ ਕਹੀਅਨਿ ਕੇਤੇ ਗਾਵਣਹਾਰੇ ॥
केते राग परी सिउ कहीअनि केते गावणहारे ॥
Keṯe rāg parī si▫o kahī▫an keṯe gāvaṇhāre.
So many Ragas, so many musicians singing there.
ਗਾਵਹਿ ਤੁਹਨੋ ਪਉਣੁ ਪਾਣੀ ਬੈਸੰਤਰੁ ਗਾਵੈ ਰਾਜਾ ਧਰਮੁ ਦੁਆਰੇ ॥
गावहि तुहनो पउणु पाणी बैसंतरु गावै राजा धरमु दुआरे ॥
Gāvahi ṯuhno pa▫uṇ pāṇī baisanṯar gāvai rājā ḏẖaram ḏu▫āre.
The praanic wind, water and fire sing; the Righteous Judge of Dharma sings at Your Door.
ਗਾਵਹਿ ਚਿਤੁ ਗੁਪਤੁ ਲਿਖਿ ਜਾਣਹਿ ਲਿਖਿ ਲਿਖਿ ਧਰਮੁ ਵੀਚਾਰੇ ॥
गावहि चितु गुपतु लिखि जाणहि लिखि लिखि धरमु वीचारे ॥
Gāvahi cẖiṯ gupaṯ likẖ jāṇėh likẖ likẖ ḏẖaram vīcẖāre.
Chitr and Gupt, the angels of the conscious and the subconscious who record actions, and the Righteous Judge of Dharma who judges this record sing.
ਗਾਵਹਿ ਈਸਰੁ ਬਰਮਾ ਦੇਵੀ ਸੋਹਨਿ ਸਦਾ ਸਵਾਰੇ ॥
गावहि ईसरु बरमा देवी सोहनि सदा सवारे ॥
Gāvahi īsar barmā ḏevī sohan saḏā savāre.
Shiva, Brahma and the Goddess of Beauty, ever adorned, sing.
ਗਾਵਹਿ ਇੰਦ ਇਦਾਸਣਿ ਬੈਠੇ ਦੇਵਤਿਆ ਦਰਿ ਨਾਲੇ ॥
गावहि इंद इदासणि बैठे देवतिआ दरि नाले ॥
Gāvahi inḏ iḏāsaṇ baiṯẖe ḏeviṯi▫ā ḏar nāle.
Indra, seated upon His Throne, sings with the deities at Your Door.
ਗਾਵਹਿ ਸਿਧ ਸਮਾਧੀ ਅੰਦਰਿ ਗਾਵਨਿ ਸਾਧ ਵਿਚਾਰੇ ॥
गावहि सिध समाधी अंदरि गावनि साध विचारे ॥
Gāvahi siḏẖ samāḏẖī anḏar gāvan sāḏẖ vicẖāre.
The Siddhas in Samaadhi sing; the Saadhus sing in contemplation.
ਗਾਵਨਿ ਜਤੀ ਸਤੀ ਸੰਤੋਖੀ ਗਾਵਹਿ ਵੀਰ ਕਰਾਰੇ ॥
गावनि जती सती संतोखी गावहि वीर करारे ॥
Gāvan jaṯī saṯī sanṯokẖī gāvahi vīr karāre.
The celibates, the fanatics, the peacefully accepting and the fearless warriors sing.
ਗਾਵਨਿ ਪੰਡਿਤ ਪੜਨਿ ਰਖੀਸਰ ਜੁਗੁ ਜੁਗੁ ਵੇਦਾ ਨਾਲੇ ॥
गावनि पंडित पड़नि रखीसर जुगु जुगु वेदा नाले ॥
Gāvan pandiṯ paṛan rakẖīsar jug jug veḏā nāle.
The Pandits, the religious scholars who recite the Vedas, with the supreme sages of all the ages, sing.
ਗਾਵਹਿ ਮੋਹਣੀਆ ਮਨੁ ਮੋਹਨਿ ਸੁਰਗਾ ਮਛ ਪਇਆਲੇ ॥
गावहि मोहणीआ मनु मोहनि सुरगा मछ पइआले ॥
Gāvahi mohṇī▫ā man mohan surgā macẖẖ pa▫i▫āle.
The Mohinis, the enchanting heavenly beauties who entice hearts in this world, in paradise, and in the underworld of the subconscious sing.
ਗਾਵਨਿ ਰਤਨ ਉਪਾਏ ਤੇਰੇ ਅਠਸਠਿ ਤੀਰਥ ਨਾਲੇ ॥
गावनि रतन उपाए तेरे अठसठि तीरथ नाले ॥
Gāvan raṯan upā▫e ṯere aṯẖsaṯẖ ṯirath nāle.
The celestial jewels created by You, and the sixty-eight holy places of pilgrimage sing.
ਗਾਵਹਿ ਜੋਧ ਮਹਾਬਲ ਸੂਰਾ ਗਾਵਹਿ ਖਾਣੀ ਚਾਰੇ ॥
गावहि जोध महाबल सूरा गावहि खाणी चारे ॥
Gāvahi joḏẖ mahābal sūrā gāvahi kẖāṇī cẖāre.
The brave and mighty warriors sing; the spiritual heroes and the four sources of creation sing.
ਗਾਵਹਿ ਖੰਡ ਮੰਡਲ ਵਰਭੰਡਾ ਕਰਿ ਕਰਿ ਰਖੇ ਧਾਰੇ ॥
गावहि खंड मंडल वरभंडा करि करि रखे धारे ॥
Gāvahi kẖand mandal varbẖandā kar kar rakẖe ḏẖāre.
The planets, solar systems and galaxies, created and arranged by Your Hand, sing.
ਸੇਈ ਤੁਧੁਨੋ ਗਾਵਹਿ ਜੋ ਤੁਧੁ ਭਾਵਨਿ ਰਤੇ ਤੇਰੇ ਭਗਤ ਰਸਾਲੇ ॥
सेई तुधुनो गावहि जो तुधु भावनि रते तेरे भगत रसाले ॥
Se▫ī ṯuḏẖuno gāvahi jo ṯuḏẖ bẖāvan raṯe ṯere bẖagaṯ rasāle.
They alone sing, who are pleasing to Your Will. Your devotees are imbued with the Nectar of Your Essence.
ਹੋਰਿ ਕੇਤੇ ਗਾਵਨਿ ਸੇ ਮੈ ਚਿਤਿ ਨ ਆਵਨਿ ਨਾਨਕੁ ਕਿਆ ਵੀਚਾਰੇ ॥
होरि केते गावनि से मै चिति न आवनि नानकु किआ वीचारे ॥
Hor keṯe gāvan se mai cẖiṯ na āvan Nānak ki▫ā vīcẖāre.
So many others sing, they do not come to mind. O Nanak, how can I consider them all?
ਸੋਈ ਸੋਈ ਸਦਾ ਸਚੁ ਸਾਹਿਬੁ ਸਾਚਾ ਸਾਚੀ ਨਾਈ ॥
सोई सोई सदा सचु साहिबु साचा साची नाई ॥
So▫ī so▫ī saḏā sacẖ sāhib sācẖā sācẖī nā▫ī.
That True Lord is True, Forever True, and True is His Name.
ਹੈ ਭੀ ਹੋਸੀ ਜਾਇ ਨ ਜਾਸੀ ਰਚਨਾ ਜਿਨਿ ਰਚਾਈ ॥
है भी होसी जाइ न जासी रचना जिनि रचाई ॥
Hai bẖī hosī jā▫e na jāsī racẖnā jin racẖā▫ī.
He is, and shall always be. He shall not depart, even when this Universe which He has created departs.
ਰੰਗੀ ਰੰਗੀ ਭਾਤੀ ਕਰਿ ਕਰਿ ਜਿਨਸੀ ਮਾਇਆ ਜਿਨਿ ਉਪਾਈ ॥
रंगी रंगी भाती करि करि जिनसी माइआ जिनि उपाई ॥
Rangī rangī bẖāṯī kar kar jinsī mā▫i▫ā jin upā▫ī.
He created the world, with its various colors, species of beings, and the variety of Maya.
ਕਰਿ ਕਰਿ ਵੇਖੈ ਕੀਤਾ ਆਪਣਾ ਜਿਵ ਤਿਸ ਦੀ ਵਡਿਆਈ ॥
करि करि वेखै कीता आपणा जिव तिस दी वडिआई ॥
Kar kar vekẖai kīṯā āpṇā jiv ṯis ḏī vadi▫ā▫ī.
Having created the creation, He watches over it Himself, by His Greatness.
ਜੋ ਤਿਸੁ ਭਾਵੈ ਸੋਈ ਕਰਸੀ ਹੁਕਮੁ ਨ ਕਰਣਾ ਜਾਈ ॥
जो तिसु भावै सोई करसी हुकमु न करणा जाई ॥
Jo ṯis bẖāvai so▫ī karsī hukam na karṇā jā▫ī.
He does whatever He pleases. No order can be issued to Him.
taken as a whole, in my understanding, all roads lead to rome,
the particular line you have quoted, intimates that those who find his will pleasing, ie, those who find that living a life of truth pleasing, sing, therefore, it is not about religion, worship, or even gods, it is merely a case of if you live by the truth, and find that pleasing, then you are one of those that sing, that accept the Creator as the ultimate truth.