Anybody is free to lend or loan bitcoins.

The loans can not extend the volume of bitcoins on the block chain, but any debt is to a degree the same as money. The safer it is, he longer maturity it has, and the more transferable it is, the more it likens to money. So even if it is not base money, the bitcoins itself, it can be a part of the supply of bitcoins and depress the price. It is unavoidable.