BACnet4Linux license changed from GPL to LGPL

Due to numerous valid inquiries and because we feel it is the right thing to do, we have changed the licensing for BACnet4Linux code from GPL to LGPL, with the exception of the keylist library and MS/TP module, which are under GPL+exception (embedded software friendly license, like the eCos project).

We hope this change enables others with userspace applications that are currently closed-source products - mostly because of NDAs for some of the already implemented communication protocols - to be able to use this codebase. Note that adding BACnet4Linux software to your proprietary code will problably require some architecture changes to the current BACnet4Linux codebase (v0.3.2) - but these kind of changes should be for the better (and are welcome).