Charging interest is not forbidden in Judaism or Christianity. There are stipulations, but it is not illegal. Jesus Christ even said usury would've been better than hiding the gift completely in the following Scripture.
Luke 19:12 KJV He said therefore, A certain nobleman went into a far country to receive for himself a kingdom, and to return. 13 And he called his ten servants, and delivered them ten pounds, and said unto them, Occupy till I come. 14 But his citizens hated him, and sent a message after him, saying, We will not have this [man] to reign over us. 15 And it came to pass, that when he was returned, having received the kingdom, then he commanded these servants to be called unto him, to whom he had given the money, that he might know how much every man had gained by trading. 16 Then came the first, saying, Lord, thy pound hath gained ten pounds. 17 And he said unto him, Well, thou good servant: because thou hast been faithful in a very little, have thou authority over ten cities. 18 And the second came, saying, Lord, thy pound hath gained five pounds. 19 And he said likewise to him, Be thou also over five cities. 20 And another came, saying, Lord, behold, [here is] thy pound, which I have kept laid up in a napkin: 21 For I feared thee, because thou art an austere man: thou takest up that thou layedst not down, and reapest that thou didst not sow. 22 And he saith unto him, Out of thine own mouth will I judge thee, [thou] wicked servant. Thou knewest that I was an austere man, taking up that I laid not down, and reaping that I did not sow: 23 Wherefore then gavest not thou my money into the bank, that at my coming I might have required mine own with usury? 24 And he said unto them that stood by, Take from him the pound, and give [it] to him that hath ten pounds. 25 (And they said unto him, Lord, he hath ten pounds.) 26 For I say unto you, That unto every one which hath shall be given; and from him that hath not, even that he hath shall be taken away from him. 27 But those mine enemies, which would not that I should reign over them, bring hither, and slay [them] before me.