@geetjacobs that’s a PRO version, there’s no public download. Only those who have a license can download it from ACF website. We are trying to find a link to ACF5 Beta (note, not PRO), it was accessible on GitHub while was under heavy development.
Here are some useful links:
Creating a new ACF field type (updated for V5, there’s a link to new template file on GitHub)
Whats new in V5
Upgrading from V4 to V5
The free version of V5 is planned for the end of 2014. But with all the HUGE respect to Elliot, it can be spring 2015 as well – he’s delaying releases on a regular basis ??
Here is a quick search for acf5 from GitHub, an ACF5 Beta fork. You can get it and check if its working. Even if that beta license is not valid anymore, with ACF5 you can use all features without a license. You just don’t receive any updates.