The Asterisk licence is the GPL with additional permissions. The GPL never restricts providing services using the software for profit (nor does it prevent your selling copies of the software (not the actual software, which you don’t own), as long as you make the source code available to those to whom you’ve provided binary versions, at no more than the actual cost of physically providing a copy, and providing you use the same licence terms).
This doesn’t apply to some codec modules, in particular G.729, for which patent licences apply. Even then, I don’t believe that there are any restrictions on providing third party services, as long as the codec is used as part of Asterisk.
This is a peer support forum, and I am not writing this for Digium.