Okay, I changed the build settings for Mac OS X to match those used by Xcode projects. The main issue seems to be the use of -D_GLIBCXX_DEBUG=1 -D_GLIBCXX_DEBUG_PEDANTIC=1 by Xcode projects. I can now successfully run and debug Xcode-built projects linked with POCO libs.
Yes, git can be compared to SVN, as you did in that thread. But github is a different beast. I think people are suggesting it because Poco needs more community:
1. Git allows community.
2. People can fork your code, make contributions, and issue a pull request (if you approve).
3. Get more adoption and visibilty.
4. Probably get more revenue.
I also think that Poco needs cleaner bug system. I would highly recommend you guys check out MongoDB. In about a year that entire project has just blown up, rapid adoption, tons of users forking and contributing bugs, and it columinated with a 4.3 million dollar funding round.