Currently, wiki hosting is being offered to non-members on a best-effort basis (“if you feel you’d make a good match”).
However, I would like this site (and others like it) to be run as a non-profit association according to Swiss law. I’m hoping that this is going to offer a number of benefits.
An association and the legal framework makes stronger assurances than just “I’m going to be a nice person and if people don’t like it, they can always fork the code and take a copy of their data elsewhere.” Now, if that’s all you need, then there’s no need to join the association. For the moment there’s no obvious drawback to not joining. In some improbable future the members of the association might decide that a particular service is going to be members-only. At that point, you can always reconsider. But in general, the association is for those people who don’t just want to entrust their wikis to a benevolent stranger on the Internet. They want to assume responsibility and choose their leadership, their hosting provider, and so on.
In fact, the legal framework makes it possible to take the current leadership to court (in Switzerland) if they are violating the articles of assembly. The articles of assembly are legally binding. Of course we all know how it is: as long as the sums are small, there’s no point in taking people to court. And that’s why there is little incentive to join the association while stakes are low. Once your wiki grows in importance, however, if you use it to make money, if you have a following, then suddenly it has more value and you’d like to have a say in how things are managed. An association allows you to do that.
The way membership fees are going to work is that the members decide upon the fee to pay the general assembly. It could be zero, it could be money to cover server costs, or one day it could be more: money to organise a conference, for example. It would always be money to be used in line with the objectives set out in the articles of association. If you don’t like the membership fees, if you think those fees are not necessary, but you were in the minority and couldn’t convince your fellow members to oust the current board, then you can always leave the association without paying the new fees. You only pay the fees if you agree to them. But then again, leaving might also entail costs, depending on how important the site has become.