Turning 'free of charge' into a noun phrase

I am helping a PhD student who makes constant reference to an Internet application he is studying by using a string of noun phrases, specifically

...its ease of use, general applicability and free of charge

By free of charge he obviously means it costs the user nothing, but it doesn't fit with the sentence grammar.

My question is how do you turn free of charge, which is adjectival, into a noun phrase? The freedom of charge is just wrong, and though free accessability works it also has another distracting meaning. Turning free into a gerund doesn't help in this case either.

In previous cases I've suggested to him a restucturing of the sentence grammar, but I'd be interested to hear some better suggestions.

Rather than shoehorning the phrase into the existing grammar, I would rewrite the sentence to read:

which is easy to use, generally applicable, and free of charge.

If I was just saying it once, I'd probably say "... and the fact that it is available free of charge ..." But some people object to the phrase "the fact that".

Another possibility is "zero cost", as in, "... its ease of use, general applicability, and zero cost ...".

"Free availability" is possible but may not be clear.

I don't think there is a noun phrase corresponding to "free of charge". "Freedom of charge"? Umm ... no. "Freedom from charge"? Maybe, but I don't think anyone says that.