Sam2 –
With all due respect, it’s a davar pashut that he is mistaken. R’ Ovadia also has a teshuva and says it’s pashut that the Ran didn’t see the Rambam and paskened the way he did from a lack of accurate information (which is clear, understanding as he lived in Christian Spain at a time when there were lots of Christians making up stories about how Islam is an idolatrous religion; you can find this all online). It is 100% mutar to enter a mosque (and daven and learn there too if you’d like).
Allah is a world which the Rambam, in his writings in Arabic, frequently uses to refer to Hashem. That’s all it means.