As further proof that it was a tax dodge, the new arrangement was not introduced in all countries at the same time. The focus was on those countries that were likely to seek tax returns, such as the USA, France, UK and some other countries. As a result, for quite a while, literature in many affluent countries was offered 'without charge' while in many 3rd world countries they still had to pay.
Although all countries now offer the literature without charge, there are still variations. In the UK, JW's are not to ask for a donation - they must wait for the recipient to mention it. In Italy, however, the KM includes requests for money in the examples of what to say at a door. In some third world countries, because the JW is also poor and cannot afford to pay at the hall without getting the money back, they still will not give literature unless a suitable 'donation' is made, except for a tract.
If a congregation does not send in donations regularly each month, they are advised that 'controlled stock' will no longer be delivered. As others have said, it is just semantics - the literature is still not free, but it gets around tax laws. If a country wants taxes, as France did, instead of paying they close down the branch and import the literature instead. So much for giving the things due to Caesar......