Google Code-in

Let's face it. Our website is terrible dated. We know that, you know that.

We want to replace it, and the first thing to know is "yes, but with what". So we're looking for a good replacement. We'd like you to look around. There's a few requirements:

1) It's free (at least for us).
2) It's open source.
3) It runs on Linux (probably all do).
4) It looks really good on desktop, tablet and mobile.
5) Doesn't contain ads or anything like that.
6) Content can be edited by someone that doesn't know or care about websites (much) for example developers that just focus on coding.
7) Has a decent search system.
8) Has roles and permissions, so we can have public and private pages, allow users to edit some pages but not all pages, and so on.
9) Plays well with search engines.
10) It's well maintained (this means new releases are published often and the last one is recent).