In exchange, we ask to be able to announce our probono collaboration (in this website, in our twitter account,…) and that you do the same. Some examples would be a mention or link in your site, a blog post announcing the move to WP and mentioning that we helped you in the process and/or publicity through your social sites (twitter, facebook, …). You don´t need to do all these things (though that would be absolutely great!) but at least some of them (and at least one before the start of the process).
*We reserve the right to freely decide which NGO/non-profit can benefit from our probono work. Third parties can be involved in the discussion (and if so we think it´s only fair they also do it probono!) but it is mandatory that the agreement to these conditions comes from a legal representative of the organization itself. Proof of the organization legal status could be requested.