We have a quite straightforward method of implementing new features.
- do a feature request for a module in the features section of the forums. (that is this discussion ) Here the community will discuss what the module is about, what benefit we have from the module.
- If someone want to install the software on a server, the next step is creating a howto in these forums in the howto section. When the howto is 100% reproducable the howto will be transferred to the wiki, where all community howto's are.
- Then, again if someone is willing (and can) the module can be created. The @dev_team is more than willing to assist with creating new modules/rpm's for NethServer.
So, if you think Kannel is a must-have for NethServer, I would say you start with installing it on NethServer. Make sure you document every step and put it in a howto. There are quite a few examples of howto's that you can have a look at so you see how a complete howto should look like.
Maybe you should look for already existing binary packages. It would make the final creation of a NS rpm a lot easier. I see there are RPM's available: http://www.kannel.org/download/1.4.4/userguide-1.4.4/userguide.html#AEN342 try install those first before you go for compile from source.
In addition of Kannel, you could have a look at playsms for sms management: https://playsms.org/about/
If you have any further question, don' t hesitate to ask!