Marshall Breeding has published his 2009 LMS survey of installed and turned over systems.
If these numbers are right, there were 634 installed systems in 2009
Of these, 265 were Koha or Evergreen, that’s 42%
In total, though, 307 were OSS LMS, that’s 48%
The biggest other player was SirsiDynix Symphony with 84 installations (13%), of which 72 of these were from Dynix and Horizon (their legacy systems).
After that, it was Apollo with 44 (7%).
I know these figures aren’t statistically absolutely accurate (and very North America biased) but, even still, these are impressive numbers for OSS LMS! I imagine they are indicative.
Going the other way, looking at the largest replaced systems, Dynix comes in top with 101 and Horizon second with 96, no real surprise there. Unicorn has 27.
Koha – Liblime has 26 but, all but one, stuck with OSS and moved to another provider. No one left Evergreen.