Is Firebird really open source as defined by OSI?
Firebird has two licenses IPL and IDPL.
IPL is derived from MPL (Mozilla Public License) which is approved by OSI. The only change is the name of Inprise corporation instead of Netscape/Mozilla.
IDPL is derived from IPL with Inprise changed to generic Initial Developer.
So, although IPL and IDPL are not OSI certified (nobody wants to pay for that), they are essentially the same as MPL and can be considered a real Open Source Licenses as defined by OSI.