A:It is permissible to allow this tower to be installed on the minaret of a musjid and to use the income for musjid expenses. The minaret is not part of the musjid, so it is like renting out an area adjacent to the musjid for purposes of income. The sanctity of the musjid will not be compromised or violated and the tower itself is not haraam but will be used for a lawful purpose.
And Allah Ta’ala knows best
Mufti Siraj Desai