Question: "Do Jesus and/or His apostles forbid practicing usury?"
Answer: Yes, in Luke 6:35, Jesus forbids usury (at least) and commands that His followers replace "lending" entirely with "giving" (at most).
Definition:
Usury (noun) is an expected return from a loan or investment in excess of the principle of the loan.
"Practicing usury" (verb) is the practice of loaning to someone under expectation or condition that the lendee returns your principle as well as an additional fee.
In either case, the thing lent and the usury on top of the loan can be a medium of exchange (money) or another piece of material wealth. It doesn't matter; for the purpose of this discussion, it's easier to talk about it all in terms of money.
Here is the text in question:
Luke 6:32-36 (emphasis mine):
In this text, Jesus explicitly tells us that, when we lend, our expectation of return should be:32 “If you love those who love you, what benefit is that to you? For even sinners love those who love them. 33 And if you do good to those who do good to you, what benefit is that to you? For even sinners do the same. 34 And if you lend to those from whom you expect to receive, what credit is that to you? Even sinners lend to sinners, to get back the same amount. 35 But love your enemies, and do good, and lend, expecting nothing in return, and your reward will be great, and you will be sons of the Most High, for he is kind to the ungrateful and the evil. 36 Be merciful, even as your Father is merciful.
Since usury is an expected return from a loan (in excess of the principle), Jesus' command categorically prohibits usury. If we are to expect nothing in return for a loan, how can we practice usury? Usury is expecting more (in point of fact, demanding more in return from a loan. If we cannot expect a return from our loans, this makes practicing usury categorically impossible."nothing"
There are two ways to interpret this passage:
(1) The straightforward interpretation essentially prohibits "lending" as such altogether, and instructs us to replace "lending" with "giving" if we are to follow Him. From now on, we don't "lend" as such. If we are not expecting "anything" in return, the proper term for what we now do is "giving. A Christian, then, doesn't lend at all, but only gives. Under this interpretation, usury is indirectly prohibited, since it is explicitly a practice enacted when lending property.
(2) The verse could be read as "Lend, expecting no return for your loan". If you want to read it this way, it sounds more like Jesus isn't prohibiting lending as such, he is merely reminding his disciples that their expectations in lending even to enemies should not be to get "a return" or "a profit". Under this interpretation, Jesus is directly addressing usury, and He is prohibiting it, but not prohibiting lending as such. His disciples can lend, but cannot expect (or demand) usury on that loan.