[andrew1]

I think 'customer' is a somewhat fair term. The fact that I use the free version of X makes it more likely that at some point I might buy the non-free version of X if I've built up a level of trust with the company, and/or that I'll recommend the product to others/at my work and they will get more users/corporate bussiness. For example I use DropBox and have almost hit the 2GB free limit. I will definitely upgrade as I really love the service, unless Dropbox do something annoying like AVG have done in this article in which case I'll find a different solution.

[msc]

She used it for years according to her blog, and doesn't mention buying a non-free version of any of their products. Becomes unhappy with the product, and doesn't mention contacting the vendor about it. Writes on her blog about how it sucks, and recommends another freeware product. I definitely wouldn't call her a customer.

[jacquesm]

You can't really blame the user for the (lack of a) businessmodel by the vendor.

If the price is 0 it does not reflect on the user at all.

Even at pricelevel '0' you can be a customer.