I remember they regenerate at a uniform rate over time, but what is that rate in HP/s?
Do all units regenerate at the same rate? Do units and building regenerate at the same rate?
Zerg units and buildings regenerate at the flat rate of approximately
0.372 hp/s or
1 hp per 2.685 sec
In comparison to SC2, the hp regen rate is the same, regardless of whether the unit is on plain terrain, on creep or burrowed.
I made a custom game in Brood War 1.16.1 (bonus points if you can name the map by the screenshots).
The game speed was set to Fastest. In Fastest game speed, one real second is 1.4 game seconds. (But since there's no in-built clock, it doesn't really matter.)
I placed 1 hydra on plain terrain, 1 hydra on creep, and I burrowed 1 hydra.
I used a Defiler's Plague to bring 3 hydras down to 1 hp each. This was the easiest way because Plague ignores armor and deals damage by synchronous time ticks. So all the hydras were taking the same damage at the same milli/microsecond.
Once plague wore off, I used a stopwatch to time how long it took to regen 10 hp.
I took 10 samples of each case. Then I averaged and rounded the results.
I also cycled through and screenshot the health of each hydra between the ticks of hp regen. All 3 hydras have 63 hp in the screenshot.
Hydralisk on creep - 10 hp / 26.85 s
Hydralisk off creep - 10 hp / 26.85 s
Burrowed Hydralisk - 10 hp / 26.85 s
Larva - 10 hp / 26.85 s
Hatchery - 10 hp 26.85 s
Since units spawn relatively quickly compared to the duration of Plague, instead of waiting for Plague's damage, I blasted an egg down from 200 hp to ~100 hp and waited.
(!) Zerg eggs do not regen hp at all.
But they have 10 armor, so they're hard to take down to begin with.
And for fun, I plagued a Kakaru =P
It also has no regen ☃