The InSSIDER utility is commercially available from Metageek - the 2.0 version (2012) was open source and is moderately useful in resolving simple channel competition problems although there are many similar applications available on the Android platform, my personal favorite is called Wifi Analyzer - it is ad supported (not in an annoying way) and runs on my phone.

The basic issue with all of these free applications is that they only display WiFi Access Point broadcasts - they can show you most common broadcast sources but will not show other broadcast signals in the 2.4GHz ISM band that may interfere with wireless data transmissions. To get a full view of the wireless spectrum I recommend (and personally use) the Metageek Wi‑Spy USB device. This is a USB wireless receiver/spectrum analyzer that can collect and display all activity in the band, not just WiFi traffic.

I have no financial interest in Metageek - I just find it a very useful product.