IX:30 - api chet suduraachaaro bhajate maam ananyabhaak saadhur eva sa mantavyah samyag vyavasito hi sah
IX:31 - kshipram bhavati dharmaatmaa shashwacchaantim nigacchati kaunteya pratijaaneehi na me bhaktah pranashyati
IX:30 - Even if the most sinful worships me, with devotion to none else, he too should indeed be regarded as righteous, for he has rightly resolved.
IX:31 - Soon he becomes righteous and attains to eternal peace; O Arjuna, know you for certain that my devotee is never destroyed.
Judaism and Islam, in particular, have declarations that only God is worthy of our worship.
May I humbly suggest that in these two verses Krsna, while agreeing with the biblical and the quranic commandment, exposes the context and, therefore, the true inner meaning?
The sinner (and the worldly man in general) worships and is devoted to a thousand objects and personalities in this world; in fact that is why he sins, for to forget God in being attached to passing phenomena is itself the worst sin.
The 'jealous God', with the compassionate intent of bringing him to the right path, visits him with mixed, varied and unexpected experiences in the form of pain and pleasure, etc.
If he realises his folly (usually by association with men of spiritual insight), and if he has the strength of will to resolve aright, he will naturally be devoted to God and God alone.
'He has rightly resolved' is not merely resolution but an application of energies or attention in the right direction.
If you turn and move towards the light, it is possible that for every two steps forward, you are pulled back one and a half.
Never mind, you are still moving forward!
One with such resolution soon becomes a devotee of God, in his own way.
An understanding of the expression 'devoted to God in his own way' offers an appreciation of the innumerable ways in which God has been attained.
In the Bhagavatam there is a lovely verse which says that people have attained God by fearing him, loving him, hating him, fighting with him or befriending him.
In fact, people have attained him in all manner of ways.
We are devoted to God in accordance with our own nature.
Thus, the freedom to worship him in any manner the seeker likes has already been granted.