Something I haven't seen mentioned yet, but did you try to simple get in contact with them to discuss the issue? Since your website is free, it might be worth

Something I haven't seen mentioned yet, but did you try to simple get in contact with them to discuss the issue? Since your website is free, it might be worth combining forces to serve your users better. I know it's hard to swallow, but in the hand what matters is that what you do is useful to people isn't it? And if your users are moving away it probably is because `some` of the things they do is right?