Yes, you certainly can do that. For the fun part, it is indeed fun to see the calls incoming and outgoing. For the maintenance part however, it can be more than a headache. The open-source software are free and is distributed and contributed by users. For most of the features of the open-source Asterisk, they are working well. However, with the current state of hacking over the internet, it is not recommended. A licensed PBX is highly recommended as they are being updated regularly by the brand. Popular brands include Sangoma FreePBX, 3CX, Emetrotel UCX, Yeastar PBX and many more.