Learn English – What does “over time” mean

Leave can be read as time off.

Parental leave is time off specifically for parents. So a parental leave policy is a policy about time off for parents.

The definition of leave as a noun can be found by scrolling down on this page: http://dictionary.reference.com/browse/leave

2- permission to be absent, as from work or military duty: The firm offers a maternity leave as part of its benefit program.

3- the time this permission lasts: 30 days' leave

"To port over" especially in the context of a computer system refers to moving functionality from one system or architecture to another. In your example:

where porting functionality over to the Zend Framework assumes that the system/program was probably written in php without the use of the zend framework and thus after rearchitecting/rewriting/moving the code to use the zend framework has resulted in better performance.