There are several bits to Rule 5, it's probably best to read it carefully.
The 500ft rule is relaxed when taking off or landing.
The 1000ft rule (previously known as 1500ft rule) / not-over-built-up-areas rule can be relaxed for T/O and Landing at a government or licenced aerodrome. Whether it applies, or is relaxed, depends upon the class of individual aircraft.
Hence, I suspect, the slight confusion.