Is LedgersSMB free software?

Yes, its Open source. The tools we use (Perl, PostsgreSQL, Apache ++) is also Open source.
Open source means that the source code of the software is available for free to everyone and you can modify the code and distribute it yourself. http://en.wikipedia.org/wiki/Open_source

Look for a place to contribute. This means not only programming, but also documentation, theme design, art work, or architectural design. Join the mailing list.

GNU GENERAL PUBLIC LICENSE Version 2
http://ledger-smb.svn.sourceforge.net/viewvc/ledger-smb/trunk/LICENSE